[tip: x86/sev] x86/sev: Use the SVSM to create a vCPU when not in VMPL0
From: tip-bot2 for Tom Lendacky
Date: Tue Jun 18 2024 - 07:05:25 EST
The following commit has been merged into the x86/sev branch of tip:
Commit-ID: d2b2931f19e48c9148909c2f45bccf21a8a83cfb
Gitweb: https://git.kernel.org/tip/d2b2931f19e48c9148909c2f45bccf21a8a83cfb
Author: Tom Lendacky <thomas.lendacky@xxxxxxx>
AuthorDate: Wed, 05 Jun 2024 10:18:48 -05:00
Committer: Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Mon, 17 Jun 2024 20:42:56 +02:00
x86/sev: Use the SVSM to create a vCPU when not in VMPL0
Using the RMPADJUST instruction, the VMSA attribute can only be changed
at VMPL0. An SVSM will be present when running at VMPL1 or a lower
privilege level.
In that case, use the SVSM_CORE_CREATE_VCPU call or the
SVSM_CORE_DESTROY_VCPU call to perform VMSA attribute changes. Use the
VMPL level supplied by the SVSM for the VMSA when starting the AP.
[ bp: Fix typo + touchups. ]
Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://lore.kernel.org/r/bcdd95ecabe9723673b9693c7f1533a2b8f17781.1717600736.git.thomas.lendacky@xxxxxxx
---
arch/x86/include/asm/sev.h | 2 +-
arch/x86/kernel/sev.c | 74 +++++++++++++++++++++++++++----------
2 files changed, 56 insertions(+), 20 deletions(-)
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 874295a..1d0b1b2 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -233,6 +233,8 @@ struct svsm_call {
#define SVSM_CORE_CALL(x) ((0ULL << 32) | (x))
#define SVSM_CORE_REMAP_CA 0
#define SVSM_CORE_PVALIDATE 1
+#define SVSM_CORE_CREATE_VCPU 2
+#define SVSM_CORE_DELETE_VCPU 3
#ifdef CONFIG_AMD_MEM_ENCRYPT
extern void __sev_es_ist_enter(struct pt_regs *regs);
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index f1d11e7..2586ba6 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -1010,22 +1010,49 @@ void snp_accept_memory(phys_addr_t start, phys_addr_t end)
set_pages_state(vaddr, npages, SNP_PAGE_STATE_PRIVATE);
}
-static int snp_set_vmsa(void *va, bool vmsa)
+static int snp_set_vmsa(void *va, void *caa, int apic_id, bool make_vmsa)
{
- u64 attrs;
+ int ret;
- /*
- * Running at VMPL0 allows the kernel to change the VMSA bit for a page
- * using the RMPADJUST instruction. However, for the instruction to
- * succeed it must target the permissions of a lesser privileged
- * (higher numbered) VMPL level, so use VMPL1 (refer to the RMPADJUST
- * instruction in the AMD64 APM Volume 3).
- */
- attrs = 1;
- if (vmsa)
- attrs |= RMPADJUST_VMSA_PAGE_BIT;
+ if (snp_vmpl) {
+ struct svsm_call call = {};
+ unsigned long flags;
+
+ local_irq_save(flags);
+
+ call.caa = this_cpu_read(svsm_caa);
+ call.rcx = __pa(va);
+
+ if (make_vmsa) {
+ /* Protocol 0, Call ID 2 */
+ call.rax = SVSM_CORE_CALL(SVSM_CORE_CREATE_VCPU);
+ call.rdx = __pa(caa);
+ call.r8 = apic_id;
+ } else {
+ /* Protocol 0, Call ID 3 */
+ call.rax = SVSM_CORE_CALL(SVSM_CORE_DELETE_VCPU);
+ }
- return rmpadjust((unsigned long)va, RMP_PG_SIZE_4K, attrs);
+ ret = svsm_perform_call_protocol(&call);
+
+ local_irq_restore(flags);
+ } else {
+ /*
+ * If the kernel runs at VMPL0, it can change the VMSA
+ * bit for a page using the RMPADJUST instruction.
+ * However, for the instruction to succeed it must
+ * target the permissions of a lesser privileged (higher
+ * numbered) VMPL level, so use VMPL1.
+ */
+ u64 attrs = 1;
+
+ if (make_vmsa)
+ attrs |= RMPADJUST_VMSA_PAGE_BIT;
+
+ ret = rmpadjust((unsigned long)va, RMP_PG_SIZE_4K, attrs);
+ }
+
+ return ret;
}
#define __ATTR_BASE (SVM_SELECTOR_P_MASK | SVM_SELECTOR_S_MASK)
@@ -1059,11 +1086,11 @@ static void *snp_alloc_vmsa_page(int cpu)
return page_address(p + 1);
}
-static void snp_cleanup_vmsa(struct sev_es_save_area *vmsa)
+static void snp_cleanup_vmsa(struct sev_es_save_area *vmsa, int apic_id)
{
int err;
- err = snp_set_vmsa(vmsa, false);
+ err = snp_set_vmsa(vmsa, NULL, apic_id, false);
if (err)
pr_err("clear VMSA page failed (%u), leaking page\n", err);
else
@@ -1074,6 +1101,7 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip)
{
struct sev_es_save_area *cur_vmsa, *vmsa;
struct ghcb_state state;
+ struct svsm_ca *caa;
unsigned long flags;
struct ghcb *ghcb;
u8 sipi_vector;
@@ -1120,6 +1148,9 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip)
if (!vmsa)
return -ENOMEM;
+ /* If an SVSM is present, the SVSM per-CPU CAA will be !NULL */
+ caa = per_cpu(svsm_caa, cpu);
+
/* CR4 should maintain the MCE value */
cr4 = native_read_cr4() & X86_CR4_MCE;
@@ -1167,11 +1198,11 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip)
* VMPL level
* SEV_FEATURES (matches the SEV STATUS MSR right shifted 2 bits)
*/
- vmsa->vmpl = 0;
+ vmsa->vmpl = snp_vmpl;
vmsa->sev_features = sev_status >> 2;
/* Switch the page over to a VMSA page now that it is initialized */
- ret = snp_set_vmsa(vmsa, true);
+ ret = snp_set_vmsa(vmsa, caa, apic_id, true);
if (ret) {
pr_err("set VMSA page failed (%u)\n", ret);
free_page((unsigned long)vmsa);
@@ -1187,7 +1218,10 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip)
vc_ghcb_invalidate(ghcb);
ghcb_set_rax(ghcb, vmsa->sev_features);
ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_AP_CREATION);
- ghcb_set_sw_exit_info_1(ghcb, ((u64)apic_id << 32) | SVM_VMGEXIT_AP_CREATE);
+ ghcb_set_sw_exit_info_1(ghcb,
+ ((u64)apic_id << 32) |
+ ((u64)snp_vmpl << 16) |
+ SVM_VMGEXIT_AP_CREATE);
ghcb_set_sw_exit_info_2(ghcb, __pa(vmsa));
sev_es_wr_ghcb_msr(__pa(ghcb));
@@ -1205,13 +1239,13 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip)
/* Perform cleanup if there was an error */
if (ret) {
- snp_cleanup_vmsa(vmsa);
+ snp_cleanup_vmsa(vmsa, apic_id);
vmsa = NULL;
}
/* Free up any previous VMSA page */
if (cur_vmsa)
- snp_cleanup_vmsa(cur_vmsa);
+ snp_cleanup_vmsa(cur_vmsa, apic_id);
/* Record the current VMSA page */
per_cpu(sev_vmsa, cpu) = vmsa;