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Proof of concept for GHCB spec addition for throttling #4

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Proof of concept for GHCB spec addition for throttling #4

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ff20959
virt/coco/sev-guest: Initialize err in handle_guest_request
deeglaze Oct 11, 2022
73d8c91
x86/sev: Interpret vmm result as throttling
deeglaze Oct 11, 2022
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6 changes: 6 additions & 0 deletions arch/x86/include/asm/sev-common.h
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Original file line number Diff line number Diff line change
Expand Up @@ -149,6 +149,12 @@ struct snp_psc_desc {
#define GHCB_SEV_ES_PROT_UNSUPPORTED 1
#define GHCB_SNP_UNSUPPORTED 2

/* Error codes from hypervisor in EXITINFO[31:0] after VMGEXIT */
#define VMGEXIT_RESULT_OK 0
#define VMGEXIT_RESULT_EXCEPTION 1
#define VMGEXIT_RESULT_BAD_INPUT 2
#define VMGEXIT_RESULT_THROTTLED 3

/* Linux-specific reason codes (used with reason set 1) */
#define SEV_TERM_SET_LINUX 1
#define GHCB_TERM_REGISTER 0 /* GHCB GPA registration failure */
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4 changes: 3 additions & 1 deletion arch/x86/kernel/sev-shared.c
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Original file line number Diff line number Diff line change
Expand Up @@ -199,7 +199,7 @@ static enum es_result verify_exception_info(struct ghcb *ghcb, struct es_em_ctxt
if (!ret)
return ES_OK;

if (ret == 1) {
if (ret == VMGEXIT_RESULT_EXCEPTION) {
u64 info = ghcb->save.sw_exit_info_2;
unsigned long v;

Expand All @@ -217,6 +217,8 @@ static enum es_result verify_exception_info(struct ghcb *ghcb, struct es_em_ctxt

return ES_EXCEPTION;
}
} else if (ret == VMGEXIT_RESULT_THROTTLED) {
return ES_RETRY;
}

return ES_VMM_ERROR;
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6 changes: 5 additions & 1 deletion arch/x86/kernel/sev.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2161,8 +2161,12 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned
}

ret = sev_es_ghcb_hv_call(ghcb, true, &ctxt, exit_code, input->req_gpa, input->resp_gpa);
if (ret)
/* ret is an es_result at this point */
if (ret) {
if (ret == ES_RETRY)
ret = -EAGAIN;
goto e_put;
}

if (ghcb->save.sw_exit_info_2) {
/* Number of expected pages are returned in RBX */
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2 changes: 1 addition & 1 deletion drivers/virt/coco/sevguest/sevguest.c
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Expand Up @@ -307,7 +307,7 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
u8 type, void *req_buf, size_t req_sz, void *resp_buf,
u32 resp_sz, __u64 *fw_err)
{
unsigned long err;
unsigned long err = 0;
u64 seqno;
int rc;

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