linux-kernel - Re: [PATCH v11 2/7] x86/sev: Change snp_guest_issue_request's fw

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Date:   Fri, 20 Jan 2023 15:09:18 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Dionna Glaze <dionnaglaze@...gle.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Tom Lendacky <Thomas.Lendacky@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Joerg Roedel <jroedel@...e.de>,
        Peter Gonda <pgonda@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Venu Busireddy <venu.busireddy@...cle.com>,
        Michael Roth <michael.roth@....com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Michael Sterritt <sterritt@...gle.com>
Subject: Re: [PATCH v11 2/7] x86/sev: Change snp_guest_issue_request's fw_err

On Wed, Jan 11, 2023 at 07:39:56PM +0000, Dionna Glaze wrote:
> The type of unsigned long also causes problems, since sw_exit_info2 is
> u64 (unsigned long long) vs the argument's unsigned long*. A temporary
> typedef is introduced for the err argument so it can be changed in a
> later patch more cleanly.

Why?

Why not make it a u64 directly and be done with it?

---

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index ebc271bb6d8e..61b0bfc7f131 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -196,7 +196,7 @@ void snp_set_memory_private(unsigned long vaddr, unsigned int npages);
 void snp_set_wakeup_secondary_cpu(void);
 bool snp_init(struct boot_params *bp);
 void __init __noreturn snp_abort(void);
-int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned long *fw_err);
+int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, u64 *exitinfo2);
 #else
 static inline void sev_es_ist_enter(struct pt_regs *regs) { }
 static inline void sev_es_ist_exit(void) { }
@@ -216,8 +216,7 @@ static inline void snp_set_memory_private(unsigned long vaddr, unsigned int npag
 static inline void snp_set_wakeup_secondary_cpu(void) { }
 static inline bool snp_init(struct boot_params *bp) { return false; }
 static inline void snp_abort(void) { }
-static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input,
-					  unsigned long *fw_err)
+static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, u64 *exitinfo2)
 {
 	return -ENOTTY;
 }
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 679026a640ef..70b4cbd33c45 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -22,6 +22,7 @@
 #include <linux/efi.h>
 #include <linux/platform_device.h>
 #include <linux/io.h>
+#include <linux/psp-sev.h>
 
 #include <asm/cpu_entry_area.h>
 #include <asm/stacktrace.h>
@@ -2175,7 +2176,7 @@ static int __init init_sev_config(char *str)
 }
 __setup("sev=", init_sev_config);
 
-int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned long *fw_err)
+int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, u64 *exitinfo2)
 {
 	struct ghcb_state state;
 	struct es_em_ctxt ctxt;
@@ -2186,9 +2187,11 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned
 	if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
 		return -ENODEV;
 
-	if (!fw_err)
+	if (!exitinfo2)
 		return -EINVAL;
 
+	*exitinfo2 = SEV_RET_NO_FW_CALL;
+
 	/*
 	 * __sev_get_ghcb() needs to run with IRQs disabled because it is using
 	 * a per-CPU GHCB.
@@ -2212,14 +2215,13 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned
 	if (ret)
 		goto e_put;
 
+	*exitinfo2 = ghcb->save.sw_exit_info_2;
 	if (ghcb->save.sw_exit_info_2) {
 		/* Number of expected pages are returned in RBX */
 		if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST &&
 		    ghcb->save.sw_exit_info_2 == SNP_GUEST_REQ_INVALID_LEN)
 			input->data_npages = ghcb_get_rbx(ghcb);
 
-		*fw_err = ghcb->save.sw_exit_info_2;
-
 		ret = -EIO;
 	}
 
diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 4ec4174e05a3..e15d94785761 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -322,8 +322,7 @@ 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;
-	u64 seqno;
+	u64 seqno, err;
 	int rc;
 
 	/* Get message sequence and verify that its a non-zero */

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette