Re: [PATCH v2 1/4] KVM: x86: Move FPU register accessors into fpu.h

From: Vitaly Kuznetsov
Date: Tue Apr 13 2021 - 09:41:18 EST

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In reply to: Siddharth Chandrasekaran: "[PATCH v2 1/4] KVM: x86: Move FPU register accessors into fpu.h"
Next in thread: Siddharth Chandrasekaran: "Re: [PATCH v2 1/4] KVM: x86: Move FPU register accessors into fpu.h"
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Siddharth Chandrasekaran <sidcha@xxxxxxxxx> writes:

> Hyper-v XMM fast hypercalls use XMM registers to pass input/output
> parameters. To access these, hyperv.c can reuse some FPU register
> accessors defined in emulator.c. Move them to a common location so both
> can access them.
>
> While at it, reorder the parameters of these accessor methods to make
> them more readable.
>
> Cc: Alexander Graf <graf@xxxxxxxxxx>
> Cc: Evgeny Iakovlev <eyakovl@xxxxxxxxx>
> Signed-off-by: Siddharth Chandrasekaran <sidcha@xxxxxxxxx>
> ---
> arch/x86/kvm/emulate.c | 138 ++++++----------------------------------
> arch/x86/kvm/fpu.h | 140 +++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 158 insertions(+), 120 deletions(-)
> create mode 100644 arch/x86/kvm/fpu.h
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index f7970ba6219f..296f8f3ce988 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -22,7 +22,6 @@
> #include "kvm_cache_regs.h"
> #include "kvm_emulate.h"
> #include <linux/stringify.h>
> -#include <asm/fpu/api.h>
> #include <asm/debugreg.h>
> #include <asm/nospec-branch.h>
>
> @@ -30,6 +29,7 @@
> #include "tss.h"
> #include "mmu.h"
> #include "pmu.h"
> +#include "fpu.h"
>
> /*
> * Operand types
> @@ -1081,116 +1081,14 @@ static void fetch_register_operand(struct operand *op)
> }
> }
>
> -static void emulator_get_fpu(void)
> -{
> - fpregs_lock();
> -
> - fpregs_assert_state_consistent();
> - if (test_thread_flag(TIF_NEED_FPU_LOAD))
> - switch_fpu_return();
> -}
> -
> -static void emulator_put_fpu(void)
> -{
> - fpregs_unlock();
> -}
> -
> -static void read_sse_reg(sse128_t *data, int reg)
> -{
> - emulator_get_fpu();
> - switch (reg) {
> - case 0: asm("movdqa %%xmm0, %0" : "=m"(*data)); break;
> - case 1: asm("movdqa %%xmm1, %0" : "=m"(*data)); break;
> - case 2: asm("movdqa %%xmm2, %0" : "=m"(*data)); break;
> - case 3: asm("movdqa %%xmm3, %0" : "=m"(*data)); break;
> - case 4: asm("movdqa %%xmm4, %0" : "=m"(*data)); break;
> - case 5: asm("movdqa %%xmm5, %0" : "=m"(*data)); break;
> - case 6: asm("movdqa %%xmm6, %0" : "=m"(*data)); break;
> - case 7: asm("movdqa %%xmm7, %0" : "=m"(*data)); break;
> -#ifdef CONFIG_X86_64
> - case 8: asm("movdqa %%xmm8, %0" : "=m"(*data)); break;
> - case 9: asm("movdqa %%xmm9, %0" : "=m"(*data)); break;
> - case 10: asm("movdqa %%xmm10, %0" : "=m"(*data)); break;
> - case 11: asm("movdqa %%xmm11, %0" : "=m"(*data)); break;
> - case 12: asm("movdqa %%xmm12, %0" : "=m"(*data)); break;
> - case 13: asm("movdqa %%xmm13, %0" : "=m"(*data)); break;
> - case 14: asm("movdqa %%xmm14, %0" : "=m"(*data)); break;
> - case 15: asm("movdqa %%xmm15, %0" : "=m"(*data)); break;
> -#endif
> - default: BUG();
> - }
> - emulator_put_fpu();
> -}
> -
> -static void write_sse_reg(sse128_t *data, int reg)
> -{
> - emulator_get_fpu();
> - switch (reg) {
> - case 0: asm("movdqa %0, %%xmm0" : : "m"(*data)); break;
> - case 1: asm("movdqa %0, %%xmm1" : : "m"(*data)); break;
> - case 2: asm("movdqa %0, %%xmm2" : : "m"(*data)); break;
> - case 3: asm("movdqa %0, %%xmm3" : : "m"(*data)); break;
> - case 4: asm("movdqa %0, %%xmm4" : : "m"(*data)); break;
> - case 5: asm("movdqa %0, %%xmm5" : : "m"(*data)); break;
> - case 6: asm("movdqa %0, %%xmm6" : : "m"(*data)); break;
> - case 7: asm("movdqa %0, %%xmm7" : : "m"(*data)); break;
> -#ifdef CONFIG_X86_64
> - case 8: asm("movdqa %0, %%xmm8" : : "m"(*data)); break;
> - case 9: asm("movdqa %0, %%xmm9" : : "m"(*data)); break;
> - case 10: asm("movdqa %0, %%xmm10" : : "m"(*data)); break;
> - case 11: asm("movdqa %0, %%xmm11" : : "m"(*data)); break;
> - case 12: asm("movdqa %0, %%xmm12" : : "m"(*data)); break;
> - case 13: asm("movdqa %0, %%xmm13" : : "m"(*data)); break;
> - case 14: asm("movdqa %0, %%xmm14" : : "m"(*data)); break;
> - case 15: asm("movdqa %0, %%xmm15" : : "m"(*data)); break;
> -#endif
> - default: BUG();
> - }
> - emulator_put_fpu();
> -}
> -
> -static void read_mmx_reg(u64 *data, int reg)
> -{
> - emulator_get_fpu();
> - switch (reg) {
> - case 0: asm("movq %%mm0, %0" : "=m"(*data)); break;
> - case 1: asm("movq %%mm1, %0" : "=m"(*data)); break;
> - case 2: asm("movq %%mm2, %0" : "=m"(*data)); break;
> - case 3: asm("movq %%mm3, %0" : "=m"(*data)); break;
> - case 4: asm("movq %%mm4, %0" : "=m"(*data)); break;
> - case 5: asm("movq %%mm5, %0" : "=m"(*data)); break;
> - case 6: asm("movq %%mm6, %0" : "=m"(*data)); break;
> - case 7: asm("movq %%mm7, %0" : "=m"(*data)); break;
> - default: BUG();
> - }
> - emulator_put_fpu();
> -}
> -
> -static void write_mmx_reg(u64 *data, int reg)
> -{
> - emulator_get_fpu();
> - switch (reg) {
> - case 0: asm("movq %0, %%mm0" : : "m"(*data)); break;
> - case 1: asm("movq %0, %%mm1" : : "m"(*data)); break;
> - case 2: asm("movq %0, %%mm2" : : "m"(*data)); break;
> - case 3: asm("movq %0, %%mm3" : : "m"(*data)); break;
> - case 4: asm("movq %0, %%mm4" : : "m"(*data)); break;
> - case 5: asm("movq %0, %%mm5" : : "m"(*data)); break;
> - case 6: asm("movq %0, %%mm6" : : "m"(*data)); break;
> - case 7: asm("movq %0, %%mm7" : : "m"(*data)); break;
> - default: BUG();
> - }
> - emulator_put_fpu();
> -}
> -
> static int em_fninit(struct x86_emulate_ctxt *ctxt)
> {
> if (ctxt->ops->get_cr(ctxt, 0) & (X86_CR0_TS | X86_CR0_EM))
> return emulate_nm(ctxt);
>
> - emulator_get_fpu();
> + kvm_fpu_get();
> asm volatile("fninit");
> - emulator_put_fpu();
> + kvm_fpu_put();
> return X86EMUL_CONTINUE;
> }
>
> @@ -1201,9 +1099,9 @@ static int em_fnstcw(struct x86_emulate_ctxt *ctxt)
> if (ctxt->ops->get_cr(ctxt, 0) & (X86_CR0_TS | X86_CR0_EM))
> return emulate_nm(ctxt);
>
> - emulator_get_fpu();
> + kvm_fpu_get();
> asm volatile("fnstcw %0": "+m"(fcw));
> - emulator_put_fpu();
> + kvm_fpu_put();
>
> ctxt->dst.val = fcw;
>
> @@ -1217,9 +1115,9 @@ static int em_fnstsw(struct x86_emulate_ctxt *ctxt)
> if (ctxt->ops->get_cr(ctxt, 0) & (X86_CR0_TS | X86_CR0_EM))
> return emulate_nm(ctxt);
>
> - emulator_get_fpu();
> + kvm_fpu_get();
> asm volatile("fnstsw %0": "+m"(fsw));
> - emulator_put_fpu();
> + kvm_fpu_put();
>
> ctxt->dst.val = fsw;
>
> @@ -1238,7 +1136,7 @@ static void decode_register_operand(struct x86_emulate_ctxt *ctxt,
> op->type = OP_XMM;
> op->bytes = 16;
> op->addr.xmm = reg;
> - read_sse_reg(&op->vec_val, reg);
> + kvm_read_sse_reg(reg, &op->vec_val);
> return;
> }
> if (ctxt->d & Mmx) {
> @@ -1289,7 +1187,7 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
> op->type = OP_XMM;
> op->bytes = 16;
> op->addr.xmm = ctxt->modrm_rm;
> - read_sse_reg(&op->vec_val, ctxt->modrm_rm);
> + kvm_read_sse_reg(ctxt->modrm_rm, &op->vec_val);
> return rc;
> }
> if (ctxt->d & Mmx) {
> @@ -1866,10 +1764,10 @@ static int writeback(struct x86_emulate_ctxt *ctxt, struct operand *op)
> op->bytes * op->count);
> break;
> case OP_XMM:
> - write_sse_reg(&op->vec_val, op->addr.xmm);
> + kvm_write_sse_reg(op->addr.xmm, &op->vec_val);
> break;
> case OP_MM:
> - write_mmx_reg(&op->mm_val, op->addr.mm);
> + kvm_write_mmx_reg(op->addr.mm, &op->mm_val);
> break;
> case OP_NONE:
> /* no writeback */
> @@ -4124,11 +4022,11 @@ static int em_fxsave(struct x86_emulate_ctxt *ctxt)
> if (rc != X86EMUL_CONTINUE)
> return rc;
>
> - emulator_get_fpu();
> + kvm_fpu_get();
>
> rc = asm_safe("fxsave %[fx]", , [fx] "+m"(fx_state));
>
> - emulator_put_fpu();
> + kvm_fpu_put();
>
> if (rc != X86EMUL_CONTINUE)
> return rc;
> @@ -4172,7 +4070,7 @@ static int em_fxrstor(struct x86_emulate_ctxt *ctxt)
> if (rc != X86EMUL_CONTINUE)
> return rc;
>
> - emulator_get_fpu();
> + kvm_fpu_get();
>
> if (size < __fxstate_size(16)) {
> rc = fxregs_fixup(&fx_state, size);
> @@ -4189,7 +4087,7 @@ static int em_fxrstor(struct x86_emulate_ctxt *ctxt)
> rc = asm_safe("fxrstor %[fx]", : [fx] "m"(fx_state));
>
> out:
> - emulator_put_fpu();
> + kvm_fpu_put();
>
> return rc;
> }
> @@ -5510,9 +5408,9 @@ static int flush_pending_x87_faults(struct x86_emulate_ctxt *ctxt)
> {
> int rc;
>
> - emulator_get_fpu();
> + kvm_fpu_get();
> rc = asm_safe("fwait");
> - emulator_put_fpu();
> + kvm_fpu_put();
>
> if (unlikely(rc != X86EMUL_CONTINUE))
> return emulate_exception(ctxt, MF_VECTOR, 0, false);
> @@ -5523,7 +5421,7 @@ static int flush_pending_x87_faults(struct x86_emulate_ctxt *ctxt)
> static void fetch_possible_mmx_operand(struct operand *op)
> {
> if (op->type == OP_MM)
> - read_mmx_reg(&op->mm_val, op->addr.mm);
> + kvm_read_mmx_reg(op->addr.mm, &op->mm_val);
> }
>
> static int fastop(struct x86_emulate_ctxt *ctxt, fastop_t fop)
> diff --git a/arch/x86/kvm/fpu.h b/arch/x86/kvm/fpu.h
> new file mode 100644
> index 000000000000..3ba12888bf66
> --- /dev/null
> +++ b/arch/x86/kvm/fpu.h
> @@ -0,0 +1,140 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef __KVM_FPU_H_
> +#define __KVM_FPU_H_
> +
> +#include <asm/fpu/api.h>
> +
> +typedef u32 __attribute__((vector_size(16))) sse128_t;

Post-patch we seem to have two definitions of 'sse128_t':

$ git grep sse128_t
HEAD~3:arch/x86/kvm/fpu.h:typedef u32 __attribute__((vector_size(16))) sse128_t;
HEAD~3:arch/x86/kvm/fpu.h:#define __sse128_u union { sse128_t vec; u64 as_u64[2]; u32 as_u32[4]; }
HEAD~3:arch/x86/kvm/fpu.h:static inline void _kvm_read_sse_reg(int reg, sse128_t *data)
HEAD~3:arch/x86/kvm/fpu.h:static inline void _kvm_write_sse_reg(int reg, const sse128_t *data)
HEAD~3:arch/x86/kvm/fpu.h:static inline void kvm_read_sse_reg(int reg, sse128_t *data)
HEAD~3:arch/x86/kvm/fpu.h:static inline void kvm_write_sse_reg(int reg, const sse128_t *data)
HEAD~3:arch/x86/kvm/kvm_emulate.h:typedef u32 __attribute__((vector_size(16))) sse128_t;
HEAD~3:arch/x86/kvm/kvm_emulate.h: char valptr[sizeof(sse128_t)];
HEAD~3:arch/x86/kvm/kvm_emulate.h: sse128_t vec_val;

Should the one from kvm_emulate.h go away?

> +#define __sse128_u union { sse128_t vec; u64 as_u64[2]; u32 as_u32[4]; }
> +#define sse128_lo(x) ({ __sse128_u t; t.vec = x; t.as_u64[0]; })
> +#define sse128_hi(x) ({ __sse128_u t; t.vec = x; t.as_u64[1]; })
> +#define sse128_l0(x) ({ __sse128_u t; t.vec = x; t.as_u32[0]; })
> +#define sse128_l1(x) ({ __sse128_u t; t.vec = x; t.as_u32[1]; })
> +#define sse128_l2(x) ({ __sse128_u t; t.vec = x; t.as_u32[2]; })
> +#define sse128_l3(x) ({ __sse128_u t; t.vec = x; t.as_u32[3]; })
> +#define sse128(lo, hi) ({ __sse128_u t; t.as_u64[0] = lo; t.as_u64[1] = hi; t.vec; })
> +
> +static inline void _kvm_read_sse_reg(int reg, sse128_t *data)
> +{
> + switch (reg) {
> + case 0: asm("movdqa %%xmm0, %0" : "=m"(*data)); break;
> + case 1: asm("movdqa %%xmm1, %0" : "=m"(*data)); break;
> + case 2: asm("movdqa %%xmm2, %0" : "=m"(*data)); break;
> + case 3: asm("movdqa %%xmm3, %0" : "=m"(*data)); break;
> + case 4: asm("movdqa %%xmm4, %0" : "=m"(*data)); break;
> + case 5: asm("movdqa %%xmm5, %0" : "=m"(*data)); break;
> + case 6: asm("movdqa %%xmm6, %0" : "=m"(*data)); break;
> + case 7: asm("movdqa %%xmm7, %0" : "=m"(*data)); break;
> +#ifdef CONFIG_X86_64
> + case 8: asm("movdqa %%xmm8, %0" : "=m"(*data)); break;
> + case 9: asm("movdqa %%xmm9, %0" : "=m"(*data)); break;
> + case 10: asm("movdqa %%xmm10, %0" : "=m"(*data)); break;
> + case 11: asm("movdqa %%xmm11, %0" : "=m"(*data)); break;
> + case 12: asm("movdqa %%xmm12, %0" : "=m"(*data)); break;
> + case 13: asm("movdqa %%xmm13, %0" : "=m"(*data)); break;
> + case 14: asm("movdqa %%xmm14, %0" : "=m"(*data)); break;
> + case 15: asm("movdqa %%xmm15, %0" : "=m"(*data)); break;
> +#endif
> + default: BUG();
> + }
> +}
> +
> +static inline void _kvm_write_sse_reg(int reg, const sse128_t *data)
> +{
> + switch (reg) {
> + case 0: asm("movdqa %0, %%xmm0" : : "m"(*data)); break;
> + case 1: asm("movdqa %0, %%xmm1" : : "m"(*data)); break;
> + case 2: asm("movdqa %0, %%xmm2" : : "m"(*data)); break;
> + case 3: asm("movdqa %0, %%xmm3" : : "m"(*data)); break;
> + case 4: asm("movdqa %0, %%xmm4" : : "m"(*data)); break;
> + case 5: asm("movdqa %0, %%xmm5" : : "m"(*data)); break;
> + case 6: asm("movdqa %0, %%xmm6" : : "m"(*data)); break;
> + case 7: asm("movdqa %0, %%xmm7" : : "m"(*data)); break;
> +#ifdef CONFIG_X86_64
> + case 8: asm("movdqa %0, %%xmm8" : : "m"(*data)); break;
> + case 9: asm("movdqa %0, %%xmm9" : : "m"(*data)); break;
> + case 10: asm("movdqa %0, %%xmm10" : : "m"(*data)); break;
> + case 11: asm("movdqa %0, %%xmm11" : : "m"(*data)); break;
> + case 12: asm("movdqa %0, %%xmm12" : : "m"(*data)); break;
> + case 13: asm("movdqa %0, %%xmm13" : : "m"(*data)); break;
> + case 14: asm("movdqa %0, %%xmm14" : : "m"(*data)); break;
> + case 15: asm("movdqa %0, %%xmm15" : : "m"(*data)); break;
> +#endif
> + default: BUG();
> + }
> +}
> +
> +static inline void _kvm_read_mmx_reg(int reg, u64 *data)
> +{
> + switch (reg) {
> + case 0: asm("movq %%mm0, %0" : "=m"(*data)); break;
> + case 1: asm("movq %%mm1, %0" : "=m"(*data)); break;
> + case 2: asm("movq %%mm2, %0" : "=m"(*data)); break;
> + case 3: asm("movq %%mm3, %0" : "=m"(*data)); break;
> + case 4: asm("movq %%mm4, %0" : "=m"(*data)); break;
> + case 5: asm("movq %%mm5, %0" : "=m"(*data)); break;
> + case 6: asm("movq %%mm6, %0" : "=m"(*data)); break;
> + case 7: asm("movq %%mm7, %0" : "=m"(*data)); break;
> + default: BUG();
> + }
> +}
> +
> +static inline void _kvm_write_mmx_reg(int reg, const u64 *data)
> +{
> + switch (reg) {
> + case 0: asm("movq %0, %%mm0" : : "m"(*data)); break;
> + case 1: asm("movq %0, %%mm1" : : "m"(*data)); break;
> + case 2: asm("movq %0, %%mm2" : : "m"(*data)); break;
> + case 3: asm("movq %0, %%mm3" : : "m"(*data)); break;
> + case 4: asm("movq %0, %%mm4" : : "m"(*data)); break;
> + case 5: asm("movq %0, %%mm5" : : "m"(*data)); break;
> + case 6: asm("movq %0, %%mm6" : : "m"(*data)); break;
> + case 7: asm("movq %0, %%mm7" : : "m"(*data)); break;
> + default: BUG();
> + }
> +}
> +
> +static inline void kvm_fpu_get(void)
> +{
> + fpregs_lock();
> +
> + fpregs_assert_state_consistent();
> + if (test_thread_flag(TIF_NEED_FPU_LOAD))
> + switch_fpu_return();
> +}
> +
> +static inline void kvm_fpu_put(void)
> +{
> + fpregs_unlock();
> +}
> +
> +static inline void kvm_read_sse_reg(int reg, sse128_t *data)
> +{
> + kvm_fpu_get();
> + _kvm_read_sse_reg(reg, data);
> + kvm_fpu_put();
> +}
> +
> +static inline void kvm_write_sse_reg(int reg, const sse128_t *data)
> +{
> + kvm_fpu_get();
> + _kvm_write_sse_reg(reg, data);
> + kvm_fpu_put();
> +}
> +
> +static inline void kvm_read_mmx_reg(int reg, u64 *data)
> +{
> + kvm_fpu_get();
> + _kvm_read_mmx_reg(reg, data);
> + kvm_fpu_put();
> +}
> +
> +static inline void kvm_write_mmx_reg(int reg, const u64 *data)
> +{
> + kvm_fpu_get();
> + _kvm_write_mmx_reg(reg, data);
> + kvm_fpu_put();
> +}
> +
> +#endif

--
Vitaly

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