[PATCH v9 22/43] x86/sev: Move MSR-based VMGEXITs for CPUID to helper

Brijesh Singh
2022-01-28T17:19:00Z

From: Michael Roth <michael.roth@amd.com>

This code will also be used later for SEV-SNP-validated CPUID code in
some cases, so move it to a common helper.

Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
arch/x86/kernel/sev-shared.c | 62 +++++++++++++++++++++---------------
1 file changed, 36 insertions(+), 26 deletions(-)

diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index 3aaef1a18ffe..633f1f93b6e1 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -194,6 +194,36 @@ enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb, bool set_ghcb_msr,
return verify_exception_info(ghcb, ctxt);
}

+static int __sev_cpuid_hv(u32 func, int reg_idx, u32 *reg)
+{
+ u64 val;
+
+ if (!reg)
+ return 0;
+
+ sev_es_wr_ghcb_msr(GHCB_CPUID_REQ(func, reg_idx));
+ VMGEXIT();
+ val = sev_es_rd_ghcb_msr();
+ if (GHCB_RESP_CODE(val) != GHCB_MSR_CPUID_RESP)
+ return -EIO;
+
+ *reg = (val >> 32);
+
+ return 0;
+}
+
+static int sev_cpuid_hv(u32 func, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
+{
+ int ret;
+
+ ret = __sev_cpuid_hv(func, GHCB_CPUID_REQ_EAX, eax);
+ ret = ret ? : __sev_cpuid_hv(func, GHCB_CPUID_REQ_EBX, ebx);
+ ret = ret ? : __sev_cpuid_hv(func, GHCB_CPUID_REQ_ECX, ecx);
+ ret = ret ? : __sev_cpuid_hv(func, GHCB_CPUID_REQ_EDX, edx);
+
+ return ret;
+}
+
/*
* Boot VC Handler - This is the first VC handler during boot, there is no GHCB
* page yet, so it only supports the MSR based communication with the
@@ -202,39 +232,19 @@ enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb, bool set_ghcb_msr,
void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code)
{
unsigned int fn = lower_bits(regs->ax, 32);
- unsigned long val;
+ u32 eax, ebx, ecx, edx;

/* Only CPUID is supported via MSR protocol */
if (exit_code != SVM_EXIT_CPUID)
goto fail;

- sev_es_wr_ghcb_msr(GHCB_CPUID_REQ(fn, GHCB_CPUID_REQ_EAX));
- VMGEXIT();
- val = sev_es_rd_ghcb_msr();
- if (GHCB_RESP_CODE(val) != GHCB_MSR_CPUID_RESP)
+ if (sev_cpuid_hv(fn, &eax, &ebx, &ecx, &edx))
goto fail;
- regs->ax = val >> 32;

- sev_es_wr_ghcb_msr(GHCB_CPUID_REQ(fn, GHCB_CPUID_REQ_EBX));
- VMGEXIT();
- val = sev_es_rd_ghcb_msr();
- if (GHCB_RESP_CODE(val) != GHCB_MSR_CPUID_RESP)
- goto fail;
- regs->bx = val >> 32;
-
- sev_es_wr_ghcb_msr(GHCB_CPUID_REQ(fn, GHCB_CPUID_REQ_ECX));
- VMGEXIT();
- val = sev_es_rd_ghcb_msr();
- if (GHCB_RESP_CODE(val) != GHCB_MSR_CPUID_RESP)
- goto fail;
- regs->cx = val >> 32;
-
- sev_es_wr_ghcb_msr(GHCB_CPUID_REQ(fn, GHCB_CPUID_REQ_EDX));
- VMGEXIT();
- val = sev_es_rd_ghcb_msr();
- if (GHCB_RESP_CODE(val) != GHCB_MSR_CPUID_RESP)
- goto fail;
- regs->dx = val >> 32;
+ regs->ax = eax;
+ regs->bx = ebx;
+ regs->cx = ecx;
+ regs->dx = edx;

/*
* This is a VC handler and the #VC is only raised when SEV-ES is
--
2.25.1