[tip: x86/sev] x86/sev: Expose sev_es_ghcb_hv_call() for use by HyperV

From: tip-bot2 for Tianyu Lan
Date: Mon Oct 25 2021 - 12:34:42 EST

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The following commit has been merged into the x86/sev branch of tip:

Commit-ID: 007faec014cb5d26983c1f86fd08c6539b41392e
Gitweb: https://git.kernel.org/tip/007faec014cb5d26983c1f86fd08c6539b41392e
Author: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
AuthorDate: Mon, 25 Oct 2021 08:21:10 -04:00
Committer: Borislav Petkov <bp@xxxxxxx>
CommitterDate: Mon, 25 Oct 2021 18:11:42 +02:00

x86/sev: Expose sev_es_ghcb_hv_call() for use by HyperV

Hyper-V needs to issue the GHCB HV call in order to read/write MSRs in
Isolation VMs. For that, expose sev_es_ghcb_hv_call().

The Hyper-V Isolation VMs are unenlightened guests and run a paravisor
at VMPL0 for communicating. GHCB pages are being allocated and set up
by that paravisor. Linux gets the GHCB page's physical address via
MSR_AMD64_SEV_ES_GHCB from the paravisor and should not change it.

Add a @set_ghcb_msr parameter to sev_es_ghcb_hv_call() to control
whether the function should set the GHCB's address prior to the call or
not and export that function for use by HyperV.

[ bp: - Massage commit message
- add a struct ghcb forward declaration to fix randconfig builds. ]

Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20211025122116.264793-6-ltykernel@xxxxxxxxx
---
arch/x86/include/asm/sev.h | 6 ++++++
arch/x86/kernel/sev-shared.c | 25 ++++++++++++++++---------
arch/x86/kernel/sev.c | 13 +++++++------
3 files changed, 29 insertions(+), 15 deletions(-)

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index fa5cd05..ec060c4 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -53,6 +53,7 @@ static inline u64 lower_bits(u64 val, unsigned int bits)

struct real_mode_header;
enum stack_type;
+struct ghcb;

/* Early IDT entry points for #VC handler */
extern void vc_no_ghcb(void);
@@ -81,6 +82,11 @@ static __always_inline void sev_es_nmi_complete(void)
__sev_es_nmi_complete();
}
extern int __init sev_es_efi_map_ghcbs(pgd_t *pgd);
+extern enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
+ bool set_ghcb_msr,
+ struct es_em_ctxt *ctxt,
+ u64 exit_code, u64 exit_info_1,
+ u64 exit_info_2);
#else
static inline void sev_es_ist_enter(struct pt_regs *regs) { }
static inline void sev_es_ist_exit(void) { }
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index 4579c38..0aacd60 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -125,10 +125,9 @@ static enum es_result verify_exception_info(struct ghcb *ghcb, struct es_em_ctxt
return ES_VMM_ERROR;
}

-static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
- struct es_em_ctxt *ctxt,
- u64 exit_code, u64 exit_info_1,
- u64 exit_info_2)
+enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb, bool set_ghcb_msr,
+ struct es_em_ctxt *ctxt, u64 exit_code,
+ u64 exit_info_1, u64 exit_info_2)
{
/* Fill in protocol and format specifiers */
ghcb->protocol_version = GHCB_PROTOCOL_MAX;
@@ -138,7 +137,14 @@ static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
ghcb_set_sw_exit_info_1(ghcb, exit_info_1);
ghcb_set_sw_exit_info_2(ghcb, exit_info_2);

- sev_es_wr_ghcb_msr(__pa(ghcb));
+ /*
+ * Hyper-V unenlightened guests use a paravisor for communicating and
+ * GHCB pages are being allocated and set up by that paravisor. Linux
+ * should not change the GHCB page's physical address.
+ */
+ if (set_ghcb_msr)
+ sev_es_wr_ghcb_msr(__pa(ghcb));
+
VMGEXIT();

return verify_exception_info(ghcb, ctxt);
@@ -418,7 +424,7 @@ static enum es_result vc_handle_ioio(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
*/
sw_scratch = __pa(ghcb) + offsetof(struct ghcb, shared_buffer);
ghcb_set_sw_scratch(ghcb, sw_scratch);
- ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_IOIO,
+ ret = sev_es_ghcb_hv_call(ghcb, true, ctxt, SVM_EXIT_IOIO,
exit_info_1, exit_info_2);
if (ret != ES_OK)
return ret;
@@ -460,7 +466,8 @@ static enum es_result vc_handle_ioio(struct ghcb *ghcb, struct es_em_ctxt *ctxt)

ghcb_set_rax(ghcb, rax);

- ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_IOIO, exit_info_1, 0);
+ ret = sev_es_ghcb_hv_call(ghcb, true, ctxt,
+ SVM_EXIT_IOIO, exit_info_1, 0);
if (ret != ES_OK)
return ret;

@@ -491,7 +498,7 @@ static enum es_result vc_handle_cpuid(struct ghcb *ghcb,
/* xgetbv will cause #GP - use reset value for xcr0 */
ghcb_set_xcr0(ghcb, 1);

- ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_CPUID, 0, 0);
+ ret = sev_es_ghcb_hv_call(ghcb, true, ctxt, SVM_EXIT_CPUID, 0, 0);
if (ret != ES_OK)
return ret;

@@ -516,7 +523,7 @@ static enum es_result vc_handle_rdtsc(struct ghcb *ghcb,
bool rdtscp = (exit_code == SVM_EXIT_RDTSCP);
enum es_result ret;

- ret = sev_es_ghcb_hv_call(ghcb, ctxt, exit_code, 0, 0);
+ ret = sev_es_ghcb_hv_call(ghcb, true, ctxt, exit_code, 0, 0);
if (ret != ES_OK)
return ret;

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 2de1f36..113d3ae 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -648,7 +648,8 @@ static enum es_result vc_handle_msr(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
ghcb_set_rdx(ghcb, regs->dx);
}

- ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_MSR, exit_info_1, 0);
+ ret = sev_es_ghcb_hv_call(ghcb, true, ctxt, SVM_EXIT_MSR,
+ exit_info_1, 0);

if ((ret == ES_OK) && (!exit_info_1)) {
regs->ax = ghcb->save.rax;
@@ -867,7 +868,7 @@ static enum es_result vc_do_mmio(struct ghcb *ghcb, struct es_em_ctxt *ctxt,

ghcb_set_sw_scratch(ghcb, ghcb_pa + offsetof(struct ghcb, shared_buffer));

- return sev_es_ghcb_hv_call(ghcb, ctxt, exit_code, exit_info_1, exit_info_2);
+ return sev_es_ghcb_hv_call(ghcb, true, ctxt, exit_code, exit_info_1, exit_info_2);
}

static enum es_result vc_handle_mmio_twobyte_ops(struct ghcb *ghcb,
@@ -1117,7 +1118,7 @@ static enum es_result vc_handle_dr7_write(struct ghcb *ghcb,

/* Using a value of 0 for ExitInfo1 means RAX holds the value */
ghcb_set_rax(ghcb, val);
- ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_WRITE_DR7, 0, 0);
+ ret = sev_es_ghcb_hv_call(ghcb, true, ctxt, SVM_EXIT_WRITE_DR7, 0, 0);
if (ret != ES_OK)
return ret;

@@ -1147,7 +1148,7 @@ static enum es_result vc_handle_dr7_read(struct ghcb *ghcb,
static enum es_result vc_handle_wbinvd(struct ghcb *ghcb,
struct es_em_ctxt *ctxt)
{
- return sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_WBINVD, 0, 0);
+ return sev_es_ghcb_hv_call(ghcb, true, ctxt, SVM_EXIT_WBINVD, 0, 0);
}

static enum es_result vc_handle_rdpmc(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
@@ -1156,7 +1157,7 @@ static enum es_result vc_handle_rdpmc(struct ghcb *ghcb, struct es_em_ctxt *ctxt

ghcb_set_rcx(ghcb, ctxt->regs->cx);

- ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_RDPMC, 0, 0);
+ ret = sev_es_ghcb_hv_call(ghcb, true, ctxt, SVM_EXIT_RDPMC, 0, 0);
if (ret != ES_OK)
return ret;

@@ -1197,7 +1198,7 @@ static enum es_result vc_handle_vmmcall(struct ghcb *ghcb,
if (x86_platform.hyper.sev_es_hcall_prepare)
x86_platform.hyper.sev_es_hcall_prepare(ghcb, ctxt->regs);

- ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_VMMCALL, 0, 0);
+ ret = sev_es_ghcb_hv_call(ghcb, true, ctxt, SVM_EXIT_VMMCALL, 0, 0);
if (ret != ES_OK)
return ret;

Next message: nicolas.ferre: "[GIT PULL] ARM: at91: dt for 5.16 #2"
Previous message: André Almeida: "Re: [PATCH v2] uapi: futex: Add a futex syscall"
In reply to: Tianyu Lan: "[PATCH V9 5/9] x86/sev-es: Expose sev_es_ghcb_hv_call() to call ghcb hv call out of sev code"
Next in thread: Tianyu Lan: "[PATCH V9 6/9] x86/hyperv: Add Write/Read MSR registers via ghcb page"
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