[PATCH v4 26/75] x86/sev-es: Add CPUID handling to #VC handler

[Joerg Roedel]

From: Tom Lendacky <thomas.lenda...@amd.com>

Handle #VC exceptions caused by CPUID instructions. These happen in
early boot code when the KASLR code checks for RDTSC.

Signed-off-by: Tom Lendacky <thomas.lenda...@amd.com>
[ jroe...@suse.de: Adapt to #VC handling framework ]
Co-developed-by: Joerg Roedel <jroe...@suse.de>
Signed-off-by: Joerg Roedel <jroe...@suse.de>
---
 arch/x86/boot/compressed/sev-es.c |  4 ++++
 arch/x86/kernel/sev-es-shared.c   | 35 +++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/arch/x86/boot/compressed/sev-es.c 
b/arch/x86/boot/compressed/sev-es.c
index 4f2fc7a85c2f..851d7af29d79 100644
--- a/arch/x86/boot/compressed/sev-es.c
+++ b/arch/x86/boot/compressed/sev-es.c
@@ -16,6 +16,7 @@
 #include <asm/trapnr.h>
 #include <asm/trap_pf.h>
 #include <asm/msr-index.h>
+#include <asm/fpu/xcr.h>
 #include <asm/ptrace.h>
 #include <asm/svm.h>
 
@@ -183,6 +184,9 @@ void do_boot_stage2_vc(struct pt_regs *regs, unsigned long 
exit_code)
        case SVM_EXIT_IOIO:
                result = vc_handle_ioio(boot_ghcb, &ctxt);
                break;
+       case SVM_EXIT_CPUID:
+               result = vc_handle_cpuid(boot_ghcb, &ctxt);
+               break;
        default:
                result = ES_UNSUPPORTED;
                break;
diff --git a/arch/x86/kernel/sev-es-shared.c b/arch/x86/kernel/sev-es-shared.c
index 66d60e34eba0..59884926fae5 100644
--- a/arch/x86/kernel/sev-es-shared.c
+++ b/arch/x86/kernel/sev-es-shared.c
@@ -432,3 +432,38 @@ static enum es_result vc_handle_ioio(struct ghcb *ghcb, 
struct es_em_ctxt *ctxt)
 
        return ret;
 }
+
+static enum es_result vc_handle_cpuid(struct ghcb *ghcb,
+                                     struct es_em_ctxt *ctxt)
+{
+       struct pt_regs *regs = ctxt->regs;
+       u32 cr4 = native_read_cr4();
+       enum es_result ret;
+
+       ghcb_set_rax(ghcb, regs->ax);
+       ghcb_set_rcx(ghcb, regs->cx);
+
+       if (cr4 & X86_CR4_OSXSAVE)
+               /* Safe to read xcr0 */
+               ghcb_set_xcr0(ghcb, xgetbv(XCR_XFEATURE_ENABLED_MASK));
+       else
+               /* 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);
+       if (ret != ES_OK)
+               return ret;
+
+       if (!(ghcb_is_valid_rax(ghcb) &&
+             ghcb_is_valid_rbx(ghcb) &&
+             ghcb_is_valid_rcx(ghcb) &&
+             ghcb_is_valid_rdx(ghcb)))
+               return ES_VMM_ERROR;
+
+       regs->ax = ghcb->save.rax;
+       regs->bx = ghcb->save.rbx;
+       regs->cx = ghcb->save.rcx;
+       regs->dx = ghcb->save.rdx;
+
+       return ES_OK;
+}
-- 
2.27.0