[PATCH v4 1/7] x86/sev: Avoid WARN()s and panic()s in early boot code

Ard Biesheuvel
2024-12-05T11:28:24Z

From: Ard Biesheuvel <ardb@kernel.org>

Using WARN() or panic() while executing from the early 1:1 mapping is
unlikely to do anything useful: the string literals are passed using
their kernel virtual addresses which are not even mapped yet. But even
if they were, calling into the printk() machinery from the early 1:1
mapped code is not going to get very far.

So drop the WARN()s entirely, and replace panic() with a deadloop.

Link: https://lore.kernel.org/all/6904c198-9047-14bb-858e-38b531589379@amd.com/T/#u
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/x86/coco/sev/core.c | 15 +++++----------
arch/x86/coco/sev/shared.c | 9 +++++----
2 files changed, 10 insertions(+), 14 deletions(-)

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index c5b0148b8c0a..499b41953e3c 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -777,15 +777,10 @@ early_set_pages_state(unsigned long vaddr, unsigned long paddr,

val = sev_es_rd_ghcb_msr();

- if (WARN(GHCB_RESP_CODE(val) != GHCB_MSR_PSC_RESP,
- "Wrong PSC response code: 0x%x\n",
- (unsigned int)GHCB_RESP_CODE(val)))
+ if (GHCB_RESP_CODE(val) != GHCB_MSR_PSC_RESP)
goto e_term;

- if (WARN(GHCB_MSR_PSC_RESP_VAL(val),
- "Failed to change page state to '%s' paddr 0x%lx error 0x%llx\n",
- op == SNP_PAGE_STATE_PRIVATE ? "private" : "shared",
- paddr, GHCB_MSR_PSC_RESP_VAL(val)))
+ if (GHCB_MSR_PSC_RESP_VAL(val))
goto e_term;

/* Page validation must be performed after changing to private */
@@ -821,7 +816,7 @@ void __head early_snp_set_memory_private(unsigned long vaddr, unsigned long padd
early_set_pages_state(vaddr, paddr, npages, SNP_PAGE_STATE_PRIVATE);
}

-void __init early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr,
+void __head early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr,
unsigned long npages)
{
/*
@@ -2361,8 +2356,8 @@ static __head void svsm_setup(struct cc_blob_sev_info *cc_info)
call.rax = SVSM_CORE_CALL(SVSM_CORE_REMAP_CA);
call.rcx = pa;
ret = svsm_perform_call_protocol(&call);
- if (ret)
- panic("Can't remap the SVSM CA, ret=%d, rax_out=0x%llx\n", ret, call.rax_out);
+ while (ret)
+ cpu_relax(); /* too early to panic */

RIP_REL_REF(boot_svsm_caa) = (struct svsm_ca *)pa;
RIP_REL_REF(boot_svsm_caa_pa) = pa;
diff --git a/arch/x86/coco/sev/shared.c b/arch/x86/coco/sev/shared.c
index 71de53194089..afb7ffc355fe 100644
--- a/arch/x86/coco/sev/shared.c
+++ b/arch/x86/coco/sev/shared.c
@@ -1243,7 +1243,7 @@ static void svsm_pval_terminate(struct svsm_pvalidate_call *pc, int ret, u64 svs
__pval_terminate(pfn, action, page_size, ret, svsm_ret);
}

-static void svsm_pval_4k_page(unsigned long paddr, bool validate)
+static void __head svsm_pval_4k_page(unsigned long paddr, bool validate)
{
struct svsm_pvalidate_call *pc;
struct svsm_call call = {};
@@ -1275,12 +1275,13 @@ static void svsm_pval_4k_page(unsigned long paddr, bool validate)

ret = svsm_perform_call_protocol(&call);
if (ret)
- svsm_pval_terminate(pc, ret, call.rax_out);
+ sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PVALIDATE);

native_local_irq_restore(flags);
}

-static void pvalidate_4k_page(unsigned long vaddr, unsigned long paddr, bool validate)
+static void __head pvalidate_4k_page(unsigned long vaddr, unsigned long paddr,
+ bool validate)
{
int ret;

@@ -1293,7 +1294,7 @@ static void pvalidate_4k_page(unsigned long vaddr, unsigned long paddr, bool val
} else {
ret = pvalidate(vaddr, RMP_PG_SIZE_4K, validate);
if (ret)
- __pval_terminate(PHYS_PFN(paddr), validate, RMP_PG_SIZE_4K, ret, 0);
+ sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PVALIDATE);
}
}

--
2.47.0.338.g60cca15819-goog