[PATCH V8 5/9] x86/sev-es: Expose sev_es_ghcb_hv_call() to call ghcb hv call out of sev code

Tianyu Lan
2021-10-21T15:41:43Z

Hyper-V needs to call ghcb hv call to write/read MSR in Isolation VM.
So expose sev_es_ghcb_hv_call() to call it in the Hyper-V code.

Hyper-V Isolation VM is unenlightened guests and run a paravisor in the
VMPL0 for communicating and GHCB pages are being allocated and set up by
that paravisor. Linux gets ghcb page pa via MSR_AMD64_SEV_ES_GHCB
from paravisor and should not change it. Add set_ghcb_msr parameter for
sev_es_ghcb_hv_call() and not set ghcb page pa when it's false.

Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
---
arch/x86/include/asm/sev.h | 12 ++++++++++++
arch/x86/kernel/sev-shared.c | 26 +++++++++++++++++---------
arch/x86/kernel/sev.c | 13 +++++++------
3 files changed, 36 insertions(+), 15 deletions(-)

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index fa5cd05d3b5b..5b7f7e2b81f7 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -81,12 +81,24 @@ 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) { }
static inline int sev_es_setup_ap_jump_table(struct real_mode_header *rmh) { return 0; }
static inline void sev_es_nmi_complete(void) { }
static inline int sev_es_efi_map_ghcbs(pgd_t *pgd) { return 0; }
+static inline enum
+es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
+ bool set_ghcb_msr, u64 exit_code,
+ u64 exit_info_1, u64 exit_info_2)
+{
+ return ES_VMM_ERROR;
+}
#endif

#endif
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index ea9abd69237e..368ed36971e3 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -124,10 +124,9 @@ 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;
@@ -137,7 +136,15 @@ 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 ghcb page pa in such case and so add set_ghcb_msr
+ * parameter.
+ */
+ if (set_ghcb_msr)
+ sev_es_wr_ghcb_msr(__pa(ghcb));
+
VMGEXIT();

return verify_exception_info(ghcb, ctxt);
@@ -417,7 +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;
@@ -459,7 +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;

@@ -490,7 +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;

@@ -515,7 +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 a6895e440bc3..bb62a1d15d6c 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;

--
2.25.1