Re: [PATCH v5 03/13] x86/sev: Use kernel provided SVSM Calling Areas
From: Borislav Petkov
Date: Thu Jun 06 2024 - 08:37:18 EST
On Wed, Jun 05, 2024 at 10:18:46AM -0500, Tom Lendacky wrote:
> The SVSM Calling Area (CA) is used to communicate between Linux and the
> SVSM. Since the firmware supplied CA for the BSP is likely to be in
> reserved memory, switch off that CA to a kernel provided CA so that access
> and use of the CA is available during boot. The CA switch is done using
> the SVSM core protocol SVSM_CORE_REMAP_CA call.
>
> An SVSM call is executed by filling out the SVSM CA and setting the proper
> register state as documented by the SVSM protocol. The SVSM is invoked by
> by requesting the hypervisor to run VMPL0.
>
> Once it is safe to allocate/reserve memory, allocate a CA for each CPU.
> After allocating the new CAs, the BSP will switch from the boot CA to the
> per-CPU CA. The CA for an AP is identified to the SVSM when creating the
> VMSA in preparation for booting the AP.
>
> Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> ---
> arch/x86/include/asm/sev-common.h | 13 ++
> arch/x86/include/asm/sev.h | 32 +++++
> arch/x86/include/uapi/asm/svm.h | 1 +
> arch/x86/kernel/sev-shared.c | 128 +++++++++++++++++-
> arch/x86/kernel/sev.c | 217 +++++++++++++++++++++++++-----
> arch/x86/mm/mem_encrypt_amd.c | 8 +-
> 6 files changed, 360 insertions(+), 39 deletions(-)
Some touchups again:
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index c101b42cb421..4145928d2874 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -290,7 +290,7 @@ void snp_accept_memory(phys_addr_t start, phys_addr_t end);
u64 snp_get_unsupported_features(u64 status);
u64 sev_get_status(void);
void sev_show_status(void);
-void snp_remap_svsm_ca(void);
+void snp_update_svsm_ca(void);
#else
static inline void sev_es_ist_enter(struct pt_regs *regs) { }
static inline void sev_es_ist_exit(void) { }
@@ -320,7 +320,7 @@ static inline void snp_accept_memory(phys_addr_t start, phys_addr_t end) { }
static inline u64 snp_get_unsupported_features(u64 status) { return 0; }
static inline u64 sev_get_status(void) { return 0; }
static inline void sev_show_status(void) { }
-static inline void snp_remap_svsm_ca(void) { }
+static inline void snp_update_svsm_ca(void) { }
#endif
#ifdef CONFIG_KVM_AMD_SEV
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index b458f3c2242a..b5110c68d241 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -246,7 +246,7 @@ static enum es_result verify_exception_info(struct ghcb *ghcb, struct es_em_ctxt
return ES_VMM_ERROR;
}
-static int process_svsm_result_codes(struct svsm_call *call)
+static inline int svsm_process_result_codes(struct svsm_call *call)
{
switch (call->rax_out) {
case SVSM_SUCCESS:
@@ -274,7 +274,7 @@ static int process_svsm_result_codes(struct svsm_call *call)
* - RAX specifies the SVSM protocol/callid as input and the return code
* as output.
*/
-static __always_inline void issue_svsm_call(struct svsm_call *call, u8 *pending)
+static __always_inline void svsm_issue_call(struct svsm_call *call, u8 *pending)
{
register unsigned long rax asm("rax") = call->rax;
register unsigned long rcx asm("rcx") = call->rcx;
@@ -310,7 +310,7 @@ static int svsm_perform_msr_protocol(struct svsm_call *call)
sev_es_wr_ghcb_msr(GHCB_MSR_VMPL_REQ_LEVEL(0));
- issue_svsm_call(call, &pending);
+ svsm_issue_call(call, &pending);
resp = sev_es_rd_ghcb_msr();
@@ -325,7 +325,7 @@ static int svsm_perform_msr_protocol(struct svsm_call *call)
if (GHCB_MSR_VMPL_RESP_VAL(resp))
return -EINVAL;
- return process_svsm_result_codes(call);
+ return svsm_process_result_codes(call);
}
static int svsm_perform_ghcb_protocol(struct ghcb *ghcb, struct svsm_call *call)
@@ -348,7 +348,7 @@ static int svsm_perform_ghcb_protocol(struct ghcb *ghcb, struct svsm_call *call)
sev_es_wr_ghcb_msr(__pa(ghcb));
- issue_svsm_call(call, &pending);
+ svsm_issue_call(call, &pending);
if (pending)
return -EINVAL;
@@ -363,7 +363,7 @@ static int svsm_perform_ghcb_protocol(struct ghcb *ghcb, struct svsm_call *call)
return -EINVAL;
}
- return process_svsm_result_codes(call);
+ return svsm_process_result_codes(call);
}
static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 6bab3244a3b9..51a0984b422c 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -161,7 +161,7 @@ struct sev_config {
* For APs, the per-CPU SVSM CA is created as part of the AP
* bringup, so this flag can be used globally for the BSP and APs.
*/
- cas_initialized : 1,
+ use_cas : 1,
__reserved : 62;
};
@@ -615,15 +615,17 @@ static __always_inline void vc_forward_exception(struct es_em_ctxt *ctxt)
/* Include code shared with pre-decompression boot stage */
#include "sev-shared.c"
-static struct svsm_ca *svsm_get_caa(void)
+static inline struct svsm_ca *svsm_get_caa(void)
{
/*
- * Use rip-relative references when called early in the boot. If
- * cas_initialized is set, then it is late in the boot and no need
- * to worry about rip-relative references.
+ * Use rIP-relative references when called early in the boot. If
+ * ->use_cas is set, then it is late in the boot and no need
+ * to worry about rIP-relative references.
*/
- return RIP_REL_REF(sev_cfg).cas_initialized ? this_cpu_read(svsm_caa)
- : RIP_REL_REF(boot_svsm_caa);
+ if (RIP_REL_REF(sev_cfg).use_cas)
+ return this_cpu_read(svsm_caa);
+ else
+ return RIP_REL_REF(boot_svsm_caa);
}
static noinstr void __sev_put_ghcb(struct ghcb_state *state)
@@ -1517,7 +1519,7 @@ void __init sev_es_init_vc_handling(void)
panic("Can't remap the SVSM CA, ret=%d, rax_out=0x%llx\n",
ret, call.rax_out);
- sev_cfg.cas_initialized = true;
+ sev_cfg.use_cas = true;
local_irq_restore(flags);
}
@@ -2443,7 +2445,7 @@ void sev_show_status(void)
pr_cont("\n");
}
-void __init snp_remap_svsm_ca(void)
+void __init snp_update_svsm_ca(void)
{
if (!snp_vmpl)
return;
diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
index 6155020e4d2d..84624ae83b71 100644
--- a/arch/x86/mm/mem_encrypt_amd.c
+++ b/arch/x86/mm/mem_encrypt_amd.c
@@ -515,7 +515,7 @@ void __init sme_early_init(void)
* Switch the SVSM CA mapping (if active) from identity mapped to
* kernel mapped.
*/
- snp_remap_svsm_ca();
+ snp_update_svsm_ca();
}
void __init mem_encrypt_free_decrypted_mem(void)
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette