Re: [PATCH v3 2/6] KVM: arm64: maintain per VM value for CTR_EL0

From: Shaoqin Huang
Date: Mon May 27 2024 - 04:38:00 EST


Hi Sebastian,

On 5/14/24 15:22, Sebastian Ott wrote:
In preparation for CTR_EL0 emulation maintain a per VM for this
s/per VM/per VM value/ would be better
register and use it where appropriate.

Signed-off-by: Sebastian Ott <sebott@xxxxxxxxxx>
Reviewed-by: Shaoqin Huang <shahuang@xxxxxxxxxx>

Thanks,
Shaoqin
---
arch/arm64/include/asm/kvm_host.h | 2 ++
arch/arm64/kvm/sys_regs.c | 21 ++++++++++++++-------
2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 212ae77eefaf..1259be5e2f3e 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -331,6 +331,8 @@ struct kvm_arch {
#define KVM_ARM_ID_REG_NUM (IDREG_IDX(sys_reg(3, 0, 0, 7, 7)) + 1)
u64 id_regs[KVM_ARM_ID_REG_NUM];
+ u64 ctr_el0;
+
/* Masks for VNCR-baked sysregs */
struct kvm_sysreg_masks *sysreg_masks;
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 41741bf4d2b2..0213c96f73f2 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -219,9 +219,9 @@ void vcpu_write_sys_reg(struct kvm_vcpu *vcpu, u64 val, int reg)
* Returns the minimum line size for the selected cache, expressed as
* Log2(bytes).
*/
-static u8 get_min_cache_line_size(bool icache)
+static u8 get_min_cache_line_size(struct kvm *kvm, bool icache)
{
- u64 ctr = read_sanitised_ftr_reg(SYS_CTR_EL0);
+ u64 ctr = kvm->arch.ctr_el0;
u8 field;
if (icache)
@@ -248,7 +248,7 @@ static u32 get_ccsidr(struct kvm_vcpu *vcpu, u32 csselr)
if (vcpu->arch.ccsidr)
return vcpu->arch.ccsidr[csselr];
- line_size = get_min_cache_line_size(csselr & CSSELR_EL1_InD);
+ line_size = get_min_cache_line_size(vcpu->kvm, csselr & CSSELR_EL1_InD);
/*
* Fabricate a CCSIDR value as the overriding value does not exist.
@@ -283,7 +283,7 @@ static int set_ccsidr(struct kvm_vcpu *vcpu, u32 csselr, u32 val)
u32 i;
if ((val & CCSIDR_EL1_RES0) ||
- line_size < get_min_cache_line_size(csselr & CSSELR_EL1_InD))
+ line_size < get_min_cache_line_size(vcpu->kvm, csselr & CSSELR_EL1_InD))
return -EINVAL;
if (!ccsidr) {
@@ -1886,7 +1886,7 @@ static bool access_ctr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
if (p->is_write)
return write_to_read_only(vcpu, p, r);
- p->regval = read_sanitised_ftr_reg(SYS_CTR_EL0);
+ p->regval = vcpu->kvm->arch.ctr_el0;
return true;
}
@@ -1906,7 +1906,7 @@ static bool access_clidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
*/
static u64 reset_clidr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
{
- u64 ctr_el0 = read_sanitised_ftr_reg(SYS_CTR_EL0);
+ u64 ctr_el0 = vcpu->kvm->arch.ctr_el0;
u64 clidr;
u8 loc;
@@ -1959,8 +1959,8 @@ static u64 reset_clidr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
static int set_clidr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
u64 val)
{
- u64 ctr_el0 = read_sanitised_ftr_reg(SYS_CTR_EL0);
u64 idc = !CLIDR_LOC(val) || (!CLIDR_LOUIS(val) && !CLIDR_LOUU(val));
+ u64 ctr_el0 = vcpu->kvm->arch.ctr_el0;
if ((val & CLIDR_EL1_RES0) || (!(ctr_el0 & CTR_EL0_IDC) && idc))
return -EINVAL;
@@ -3557,6 +3557,13 @@ void kvm_reset_sys_regs(struct kvm_vcpu *vcpu)
struct kvm *kvm = vcpu->kvm;
unsigned long i;
+ if (!kvm_vcpu_initialized(vcpu))
+ /*
+ * Make sure CTR_EL0 is initialized before registers
+ * that depend on it are reset.
+ */
+ kvm->arch.ctr_el0 = read_sanitised_ftr_reg(SYS_CTR_EL0);
+
for (i = 0; i < ARRAY_SIZE(sys_reg_descs); i++) {
const struct sys_reg_desc *r = &sys_reg_descs[i];

--
Shaoqin