[PATCH -v3 00/11] SEV: Cleanup sev-guest a bit and add throttling

[PATCH -v3 00/11] SEV: Cleanup sev-guest a bit and add throttling

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Hi,

ok, here's v3, rebased ontop of -rc1 and hopefully with all the stuff
addressed. There's always room for improvement but that should come
later and ontop.

Thx.

Changelog:
----------

v2:

ok, here's v2 with the pending stuff fixed.

Thx.

v1:
---
so I've been looking at Dionna's patches adding the SEV guest throttling
and that request issuing spaghetti was getting on my nerves. And it
would've become even worse with more stuff piling ontop so here's
a first round of cleanups before adding more stuff and making it an
unmaintainable mess.

The final result is a lot easier to read with proper separation of
functionality between functions. I want to get rid of more input/output
params being passed back'n'forth and use a struct instead and Nikunj's
patches have stuff which goes in that direction but first things first.

After the cleanup, the new stuff being added is a lot less code and
almost trivial. But I've been staring at this for a while now so it
could be only me who thinks it is trivial now. But we'll see.

Initial smoke testing seems to work ok but I might've introduced some
funky bugs, ofc.

Comments and suggestions are appreciated, as always.

Thanks and thanks, Tom, for the help!


Borislav Petkov (AMD) (7):
  virt/coco/sev-guest: Check SEV_SNP attribute at probe time
  virt/coco/sev-guest: Simplify extended guest request handling
  virt/coco/sev-guest: Remove the disable_vmpck label in
    handle_guest_request()
  virt/coco/sev-guest: Carve out the request issuing logic into a helper
  virt/coco/sev-guest: Do some code style cleanups
  virt/coco/sev-guest: Convert the sw_exit_info_2 checking to a
    switch-case
  crypto: ccp: Get rid of __sev_platform_init_locked()'s local function
    pointer

Dionna Glaze (3):
  virt/coco/sev-guest: Add throttling awareness
  virt/coco/sev-guest: Double-buffer messages
  x86/sev: Change snp_guest_issue_request()'s fw_err argument

Peter Gonda (1):
  crypto: ccp - Name -1 return value as SEV_RET_NO_FW_CALL

 Documentation/virt/coco/sev-guest.rst   |  20 ++-
 arch/x86/include/asm/sev-common.h       |   3 -
 arch/x86/include/asm/sev.h              |  10 +-
 arch/x86/kernel/sev.c                   |  33 ++--
 drivers/crypto/ccp/sev-dev.c            |  22 ++-
 drivers/virt/coco/sev-guest/sev-guest.c | 190 +++++++++++++++---------
 include/uapi/linux/psp-sev.h            |   7 +
 include/uapi/linux/sev-guest.h          |  18 ++-
 8 files changed, 199 insertions(+), 104 deletions(-)

-- 
2.35.1

[PATCH -v3 01/11] crypto: ccp - Name -1 return value as SEV_RET_NO_FW_CALL

[Borislav Petkov]

From: Peter Gonda <pgonda@google.com>

The PSP can return a "firmware error" code of -1 in circumstances where
the PSP has not actually been called. To make this protocol unambiguous,
name the value SEV_RET_NO_FW_CALL.

  [ bp: Massage a bit. ]

Signed-off-by: Peter Gonda <pgonda@google.com>
Signed-off-by: Dionna Glaze <dionnaglaze@google.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
Link: https://lore.kernel.org/r/20221207010210.2563293-2-dionnaglaze@google.com
---
 Documentation/virt/coco/sev-guest.rst | 4 ++--
 drivers/crypto/ccp/sev-dev.c          | 8 +++++---
 include/uapi/linux/psp-sev.h          | 7 +++++++
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/Documentation/virt/coco/sev-guest.rst b/Documentation/virt/coco/sev-guest.rst
index bf593e88cfd9..aa3e4c6a1f90 100644
--- a/Documentation/virt/coco/sev-guest.rst
+++ b/Documentation/virt/coco/sev-guest.rst
@@ -40,8 +40,8 @@ along with a description:
 The guest ioctl should be issued on a file descriptor of the /dev/sev-guest device.
 The ioctl accepts struct snp_user_guest_request. The input and output structure is
 specified through the req_data and resp_data field respectively. If the ioctl fails
-to execute due to a firmware error, then fw_err code will be set otherwise the
-fw_err will be set to 0x00000000000000ff.
+to execute due to a firmware error, then fw_err code will be set. Otherwise, fw_err
+will be set to 0x00000000ffffffff, i.e., the lower 32-bits are -1.
 
 The firmware checks that the message sequence counter is one greater than
 the guests message sequence counter. If guest driver fails to increment message
diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index e2f25926eb51..823c67a43c38 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -444,10 +444,10 @@ static int __sev_init_ex_locked(int *error)
 
 static int __sev_platform_init_locked(int *error)
 {
+	int rc = 0, psp_ret = SEV_RET_NO_FW_CALL;
 	struct psp_device *psp = psp_master;
-	struct sev_device *sev;
-	int rc = 0, psp_ret = -1;
 	int (*init_function)(int *error);
+	struct sev_device *sev;
 
 	if (!psp || !psp->sev_data)
 		return -ENODEV;
@@ -475,9 +475,11 @@ static int __sev_platform_init_locked(int *error)
 		 * initialization function should succeed by replacing the state
 		 * with a reset state.
 		 */
-		dev_err(sev->dev, "SEV: retrying INIT command because of SECURE_DATA_INVALID error. Retrying once to reset PSP SEV state.");
+		dev_err(sev->dev,
+"SEV: retrying INIT command because of SECURE_DATA_INVALID error. Retrying once to reset PSP SEV state.");
 		rc = init_function(&psp_ret);
 	}
+
 	if (error)
 		*error = psp_ret;
 
diff --git a/include/uapi/linux/psp-sev.h b/include/uapi/linux/psp-sev.h
index 91b4c63d5cbf..1c9da485318f 100644
--- a/include/uapi/linux/psp-sev.h
+++ b/include/uapi/linux/psp-sev.h
@@ -36,6 +36,13 @@ enum {
  * SEV Firmware status code
  */
 typedef enum {
+	/*
+	 * This error code is not in the SEV spec. Its purpose is to convey that
+	 * there was an error that prevented the SEV firmware from being called.
+	 * The SEV API error codes are 16 bits, so the -1 value will not overlap
+	 * with possible values from the specification.
+	 */
+	SEV_RET_NO_FW_CALL = -1,
 	SEV_RET_SUCCESS = 0,
 	SEV_RET_INVALID_PLATFORM_STATE,
 	SEV_RET_INVALID_GUEST_STATE,
-- 
2.35.1

[PATCH -v3 02/11] virt/coco/sev-guest: Check SEV_SNP attribute at probe time

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

No need to check it on every ioctl. And yes, this is a common SEV driver
but it does only SNP-specific operations currently. This can be
revisited later, when more use cases appear.

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/kernel/sev.c                   | 3 ---
 drivers/virt/coco/sev-guest/sev-guest.c | 3 +++
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 679026a640ef..c644c34372e8 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -2183,9 +2183,6 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned
 	struct ghcb *ghcb;
 	int ret;
 
-	if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
-		return -ENODEV;
-
 	if (!fw_err)
 		return -EINVAL;
 
diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 7b4e9009f335..ed5d6ae1a144 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -703,6 +703,9 @@ static int __init sev_guest_probe(struct platform_device *pdev)
 	void __iomem *mapping;
 	int ret;
 
+	if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
+		return -ENODEV;
+
 	if (!dev->platform_data)
 		return -ENODEV;
 
-- 
2.35.1

[PATCH -v3 03/11] virt/coco/sev-guest: Simplify extended guest request handling

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Return a specific error code - -ENOSPC - to signal the too small cert
data buffer instead of checking exit code and exitinfo2.

While at it, hoist the *fw_err assignment in snp_issue_guest_request()
so that a proper error value is returned to the callers.

  [ Tom: check override_err instead of err. ]

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/kernel/sev.c                   | 11 +++---
 drivers/virt/coco/sev-guest/sev-guest.c | 48 +++++++++++++------------
 2 files changed, 32 insertions(+), 27 deletions(-)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index c644c34372e8..6a3e1425ba17 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -2209,15 +2209,16 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned
 	if (ret)
 		goto e_put;
 
+	*fw_err = 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)
+		    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;
+			ret = -ENOSPC;
+		} else {
+			ret = -EIO;
+		}
 	}
 
 e_put:
diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index ed5d6ae1a144..e61db0b15b7a 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -322,7 +322,8 @@ 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, override_err = 0;
+	unsigned int override_npages = 0;
 	u64 seqno;
 	int rc;
 
@@ -338,6 +339,7 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 	if (rc)
 		return rc;
 
+retry_request:
 	/*
 	 * Call firmware to process the request. In this function the encrypted
 	 * message enters shared memory with the host. So after this call the
@@ -346,17 +348,24 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 	 */
 	rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
 
-	/*
-	 * If the extended guest request fails due to having too small of a
-	 * certificate data buffer, retry the same guest request without the
-	 * extended data request in order to increment the sequence number
-	 * and thus avoid IV reuse.
-	 */
-	if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST &&
-	    err == SNP_GUEST_REQ_INVALID_LEN) {
-		const unsigned int certs_npages = snp_dev->input.data_npages;
+	switch (rc) {
+	case -ENOSPC:
+		/*
+		 * If the extended guest request fails due to having too
+		 * small of a certificate data buffer, retry the same
+		 * guest request without the extended data request in
+		 * order to increment the sequence number and thus avoid
+		 * IV reuse.
+		 */
+		override_npages = snp_dev->input.data_npages;
+		exit_code	= SVM_VMGEXIT_GUEST_REQUEST;
 
-		exit_code = SVM_VMGEXIT_GUEST_REQUEST;
+		/*
+		 * Override the error to inform callers the given extended
+		 * request buffer size was too small and give the caller the
+		 * required buffer size.
+		 */
+		override_err	= SNP_GUEST_REQ_INVALID_LEN;
 
 		/*
 		 * If this call to the firmware succeeds, the sequence number can
@@ -366,15 +375,7 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 		 * of the VMPCK and the error code being propagated back to the
 		 * user as an ioctl() return code.
 		 */
-		rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
-
-		/*
-		 * Override the error to inform callers the given extended
-		 * request buffer size was too small and give the caller the
-		 * required buffer size.
-		 */
-		err = SNP_GUEST_REQ_INVALID_LEN;
-		snp_dev->input.data_npages = certs_npages;
+		goto retry_request;
 	}
 
 	/*
@@ -386,7 +387,10 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 	snp_inc_msg_seqno(snp_dev);
 
 	if (fw_err)
-		*fw_err = err;
+		*fw_err = override_err ?: err;
+
+	if (override_npages)
+		snp_dev->input.data_npages = override_npages;
 
 	/*
 	 * If an extended guest request was issued and the supplied certificate
@@ -394,7 +398,7 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 	 * prevent IV reuse. If the standard request was successful, return -EIO
 	 * back to the caller as would have originally been returned.
 	 */
-	if (!rc && err == SNP_GUEST_REQ_INVALID_LEN)
+	if (!rc && override_err == SNP_GUEST_REQ_INVALID_LEN)
 		return -EIO;
 
 	if (rc) {
-- 
2.35.1

[PATCH -v3 04/11] virt/coco/sev-guest: Remove the disable_vmpck label in handle_guest_request()

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Call the function directly instead.

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 drivers/virt/coco/sev-guest/sev-guest.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index e61db0b15b7a..a51bd4afd5ab 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -405,7 +405,8 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 		dev_alert(snp_dev->dev,
 			  "Detected error from ASP request. rc: %d, fw_err: %llu\n",
 			  rc, *fw_err);
-		goto disable_vmpck;
+		snp_disable_vmpck(snp_dev);
+		return rc;
 	}
 
 	rc = verify_and_dec_payload(snp_dev, resp_buf, resp_sz);
@@ -413,14 +414,11 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 		dev_alert(snp_dev->dev,
 			  "Detected unexpected decode failure from ASP. rc: %d\n",
 			  rc);
-		goto disable_vmpck;
+		snp_disable_vmpck(snp_dev);
+		return rc;
 	}
 
 	return 0;
-
-disable_vmpck:
-	snp_disable_vmpck(snp_dev);
-	return rc;
 }
 
 static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
-- 
2.35.1

[PATCH -v3 05/11] virt/coco/sev-guest: Carve out the request issuing logic into a helper

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

This makes the code flow a lot easier to follow.

No functional changes.

  [ Tom: touchups. ]

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 drivers/virt/coco/sev-guest/sev-guest.c | 44 +++++++++++++++----------
 1 file changed, 27 insertions(+), 17 deletions(-)

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index a51bd4afd5ab..07dafe22b27a 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -318,27 +318,12 @@ static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8
 	return __enc_payload(snp_dev, req, payload, sz);
 }
 
-static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
-				u8 type, void *req_buf, size_t req_sz, void *resp_buf,
-				u32 resp_sz, __u64 *fw_err)
+static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, __u64 *fw_err)
 {
 	unsigned long err, override_err = 0;
 	unsigned int override_npages = 0;
-	u64 seqno;
 	int rc;
 
-	/* Get message sequence and verify that its a non-zero */
-	seqno = snp_get_msg_seqno(snp_dev);
-	if (!seqno)
-		return -EIO;
-
-	memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
-
-	/* Encrypt the userspace provided payload */
-	rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
-	if (rc)
-		return rc;
-
 retry_request:
 	/*
 	 * Call firmware to process the request. In this function the encrypted
@@ -347,7 +332,6 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 	 * prevent reuse of the IV.
 	 */
 	rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
-
 	switch (rc) {
 	case -ENOSPC:
 		/*
@@ -401,7 +385,33 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 	if (!rc && override_err == SNP_GUEST_REQ_INVALID_LEN)
 		return -EIO;
 
+	return rc;
+}
+
+static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
+				u8 type, void *req_buf, size_t req_sz, void *resp_buf,
+				u32 resp_sz, __u64 *fw_err)
+{
+	u64 seqno;
+	int rc;
+
+	/* Get message sequence and verify that its a non-zero */
+	seqno = snp_get_msg_seqno(snp_dev);
+	if (!seqno)
+		return -EIO;
+
+	memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
+
+	/* Encrypt the userspace provided payload */
+	rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
+	if (rc)
+		return rc;
+
+	rc = __handle_guest_request(snp_dev, exit_code, fw_err);
 	if (rc) {
+		if (rc == -EIO && *fw_err == SNP_GUEST_REQ_INVALID_LEN)
+			return rc;
+
 		dev_alert(snp_dev->dev,
 			  "Detected error from ASP request. rc: %d, fw_err: %llu\n",
 			  rc, *fw_err);
-- 
2.35.1

[PATCH -v3 06/11] virt/coco/sev-guest: Do some code style cleanups

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Remove unnecessary linebreaks, make the code more compact.

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 drivers/virt/coco/sev-guest/sev-guest.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 07dafe22b27a..81a53c31ff46 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -412,18 +412,14 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 		if (rc == -EIO && *fw_err == SNP_GUEST_REQ_INVALID_LEN)
 			return rc;
 
-		dev_alert(snp_dev->dev,
-			  "Detected error from ASP request. rc: %d, fw_err: %llu\n",
-			  rc, *fw_err);
+		dev_alert(snp_dev->dev, "Detected error from ASP request. rc: %d, fw_err: %llu\n", rc, *fw_err);
 		snp_disable_vmpck(snp_dev);
 		return rc;
 	}
 
 	rc = verify_and_dec_payload(snp_dev, resp_buf, resp_sz);
 	if (rc) {
-		dev_alert(snp_dev->dev,
-			  "Detected unexpected decode failure from ASP. rc: %d\n",
-			  rc);
+		dev_alert(snp_dev->dev, "Detected unexpected decode failure from ASP. rc: %d\n", rc);
 		snp_disable_vmpck(snp_dev);
 		return rc;
 	}
-- 
2.35.1

[PATCH -v3 07/11] virt/coco/sev-guest: Convert the sw_exit_info_2 checking to a switch-case

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

snp_issue_guest_request() checks the value returned by the hypervisor in
sw_exit_info_2 and returns a different error depending on it.

Convert those checks into a switch-case to make it more readable when
more error values are going to be checked in the future.

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/kernel/sev.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 6a3e1425ba17..d67884fb38c1 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -2210,15 +2210,21 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned
 		goto e_put;
 
 	*fw_err = ghcb->save.sw_exit_info_2;
-	if (ghcb->save.sw_exit_info_2) {
+	switch (*fw_err) {
+	case 0:
+		break;
+
+	case SNP_GUEST_REQ_INVALID_LEN:
 		/* 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) {
+		if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST) {
 			input->data_npages = ghcb_get_rbx(ghcb);
 			ret = -ENOSPC;
-		} else {
-			ret = -EIO;
+			break;
 		}
+		fallthrough;
+	default:
+		ret = -EIO;
+		break;
 	}
 
 e_put:
-- 
2.35.1

[PATCH -v3 08/11] crypto: ccp: Get rid of __sev_platform_init_locked()'s local function pointer

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Add a wrapper instead.

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 drivers/crypto/ccp/sev-dev.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 823c67a43c38..e346c00b132a 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -442,11 +442,18 @@ static int __sev_init_ex_locked(int *error)
 	return __sev_do_cmd_locked(SEV_CMD_INIT_EX, &data, error);
 }
 
+static inline int __sev_do_init_locked(int *psp_ret)
+{
+	if (sev_init_ex_buffer)
+		return __sev_init_ex_locked(psp_ret);
+	else
+		return __sev_init_locked(psp_ret);
+}
+
 static int __sev_platform_init_locked(int *error)
 {
 	int rc = 0, psp_ret = SEV_RET_NO_FW_CALL;
 	struct psp_device *psp = psp_master;
-	int (*init_function)(int *error);
 	struct sev_device *sev;
 
 	if (!psp || !psp->sev_data)
@@ -458,15 +465,12 @@ static int __sev_platform_init_locked(int *error)
 		return 0;
 
 	if (sev_init_ex_buffer) {
-		init_function = __sev_init_ex_locked;
 		rc = sev_read_init_ex_file();
 		if (rc)
 			return rc;
-	} else {
-		init_function = __sev_init_locked;
 	}
 
-	rc = init_function(&psp_ret);
+	rc = __sev_do_init_locked(&psp_ret);
 	if (rc && psp_ret == SEV_RET_SECURE_DATA_INVALID) {
 		/*
 		 * Initialization command returned an integrity check failure
@@ -477,7 +481,7 @@ static int __sev_platform_init_locked(int *error)
 		 */
 		dev_err(sev->dev,
 "SEV: retrying INIT command because of SECURE_DATA_INVALID error. Retrying once to reset PSP SEV state.");
-		rc = init_function(&psp_ret);
+		rc = __sev_do_init_locked(&psp_ret);
 	}
 
 	if (error)
-- 
2.35.1

[PATCH -v3 09/11] virt/coco/sev-guest: Add throttling awareness

[Borislav Petkov]

From: Dionna Glaze <dionnaglaze@google.com>

A potentially malicious SEV guest can constantly hammer the hypervisor
using this driver to send down requests and thus prevent or at least
considerably hinder other guests from issuing requests to the secure
processor which is a shared platform resource.

Therefore, the host is permitted and encouraged to throttle such guest
requests.

Add the capability to handle the case when the hypervisor throttles
excessive numbers of requests issued by the guest. Otherwise, the VM
platform communication key will be disabled, preventing the guest from
attesting itself.

Realistically speaking, a well-behaved guest should not even care about
throttling. During its lifetime, it would end up issuing a handful of
requests which the hardware can easily handle.

This is more to address the case of a malicious guest. Such guest should
get throttled and if its VMPCK gets disabled, then that's its own
wrongdoing and perhaps that guest even deserves it.

To the implementation: the hypervisor signals with SNP_GUEST_REQ_ERR_BUSY
that the guest requests should be throttled. That error code is returned
in the upper 32-bit half of exitinfo2 and this is part of the GHCB spec
v2.

So the guest is given a throttling period of 1 minute in which it
retries the request every 2 seconds. This is a good default but if it
turns out to not pan out in practice, it can be tweaked later.

For safety, since the encryption algorithm in GHCBv2 is AES_GCM, control
must remain in the kernel to complete the request with the current
sequence number. Returning without finishing the request allows the
guest to make another request but with different message contents. This
is IV reuse, and breaks cryptographic protections.

  [ bp: Rewrite commit message and do a simplified version. ]

Fixes: d5af44dde546 ("x86/sev: Provide support for SNP guest request NAEs")
Signed-off-by: Dionna Glaze <dionnaglaze@google.com>
Co-developed-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230214164638.1189804-2-dionnaglaze@google.com
---
 arch/x86/include/asm/sev-common.h       |  3 ++-
 arch/x86/kernel/sev.c                   |  4 ++++
 drivers/virt/coco/sev-guest/sev-guest.c | 19 ++++++++++++++++++-
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
index b8357d6ecd47..b63be696b776 100644
--- a/arch/x86/include/asm/sev-common.h
+++ b/arch/x86/include/asm/sev-common.h
@@ -128,8 +128,9 @@ struct snp_psc_desc {
 	struct psc_entry entries[VMGEXIT_PSC_MAX_ENTRY];
 } __packed;
 
-/* Guest message request error code */
+/* Guest message request error codes */
 #define SNP_GUEST_REQ_INVALID_LEN	BIT_ULL(32)
+#define SNP_GUEST_REQ_ERR_BUSY		BIT_ULL(33)
 
 #define GHCB_MSR_TERM_REQ		0x100
 #define GHCB_MSR_TERM_REASON_SET_POS	12
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index d67884fb38c1..3f664ab277c4 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -2214,6 +2214,10 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned
 	case 0:
 		break;
 
+	case SNP_GUEST_REQ_ERR_BUSY:
+		ret = -EAGAIN;
+		break;
+
 	case SNP_GUEST_REQ_INVALID_LEN:
 		/* Number of expected pages are returned in RBX */
 		if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST) {
diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 81a53c31ff46..46f1a8d558b0 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -31,6 +31,9 @@
 #define AAD_LEN		48
 #define MSG_HDR_VER	1
 
+#define SNP_REQ_MAX_RETRY_DURATION	(60*HZ)
+#define SNP_REQ_RETRY_DELAY		(2*HZ)
+
 struct snp_guest_crypto {
 	struct crypto_aead *tfm;
 	u8 *iv, *authtag;
@@ -320,7 +323,8 @@ static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8
 
 static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, __u64 *fw_err)
 {
-	unsigned long err, override_err = 0;
+	unsigned long err = 0xff, override_err = 0;
+	unsigned long req_start = jiffies;
 	unsigned int override_npages = 0;
 	int rc;
 
@@ -360,6 +364,19 @@ static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
 		 * user as an ioctl() return code.
 		 */
 		goto retry_request;
+
+	/*
+	 * The host may return SNP_GUEST_REQ_ERR_EBUSY if the request has been
+	 * throttled. Retry in the driver to avoid returning and reusing the
+	 * message sequence number on a different message.
+	 */
+	case -EAGAIN:
+		if (jiffies - req_start > SNP_REQ_MAX_RETRY_DURATION) {
+			rc = -ETIMEDOUT;
+			break;
+		}
+		schedule_timeout_killable(SNP_REQ_RETRY_DELAY);
+		goto retry_request;
 	}
 
 	/*
-- 
2.35.1

[PATCH -v3 10/11] virt/coco/sev-guest: Double-buffer messages

[Borislav Petkov]

From: Dionna Glaze <dionnaglaze@google.com>

The encryption algorithms read and write directly to shared unencrypted
memory, which may leak information as well as permit the host to tamper
with the message integrity. Instead, copy whole messages in or out as
needed before doing any computation on them.

Fixes: d5af44dde546 ("x86/sev: Provide support for SNP guest request NAEs")
Signed-off-by: Dionna Glaze <dionnaglaze@google.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230214164638.1189804-3-dionnaglaze@google.com
---
 drivers/virt/coco/sev-guest/sev-guest.c | 27 +++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 46f1a8d558b0..0c7b47acba2a 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -46,7 +46,15 @@ struct snp_guest_dev {
 
 	void *certs_data;
 	struct snp_guest_crypto *crypto;
+	/* request and response are in unencrypted memory */
 	struct snp_guest_msg *request, *response;
+
+	/*
+	 * Avoid information leakage by double-buffering shared messages
+	 * in fields that are in regular encrypted memory.
+	 */
+	struct snp_guest_msg secret_request, secret_response;
+
 	struct snp_secrets_page_layout *layout;
 	struct snp_req_data input;
 	u32 *os_area_msg_seqno;
@@ -266,14 +274,17 @@ static int dec_payload(struct snp_guest_dev *snp_dev, struct snp_guest_msg *msg,
 static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload, u32 sz)
 {
 	struct snp_guest_crypto *crypto = snp_dev->crypto;
-	struct snp_guest_msg *resp = snp_dev->response;
-	struct snp_guest_msg *req = snp_dev->request;
+	struct snp_guest_msg *resp = &snp_dev->secret_response;
+	struct snp_guest_msg *req = &snp_dev->secret_request;
 	struct snp_guest_msg_hdr *req_hdr = &req->hdr;
 	struct snp_guest_msg_hdr *resp_hdr = &resp->hdr;
 
 	dev_dbg(snp_dev->dev, "response [seqno %lld type %d version %d sz %d]\n",
 		resp_hdr->msg_seqno, resp_hdr->msg_type, resp_hdr->msg_version, resp_hdr->msg_sz);
 
+	/* Copy response from shared memory to encrypted memory. */
+	memcpy(resp, snp_dev->response, sizeof(*resp));
+
 	/* Verify that the sequence counter is incremented by 1 */
 	if (unlikely(resp_hdr->msg_seqno != (req_hdr->msg_seqno + 1)))
 		return -EBADMSG;
@@ -297,7 +308,7 @@ static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload,
 static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8 type,
 			void *payload, size_t sz)
 {
-	struct snp_guest_msg *req = snp_dev->request;
+	struct snp_guest_msg *req = &snp_dev->secret_request;
 	struct snp_guest_msg_hdr *hdr = &req->hdr;
 
 	memset(req, 0, sizeof(*req));
@@ -417,13 +428,21 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 	if (!seqno)
 		return -EIO;
 
+	/* Clear shared memory's response for the host to populate. */
 	memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
 
-	/* Encrypt the userspace provided payload */
+	/* Encrypt the userspace provided payload in snp_dev->secret_request. */
 	rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
 	if (rc)
 		return rc;
 
+	/*
+	 * Write the fully encrypted request to the shared unencrypted
+	 * request page.
+	 */
+	memcpy(snp_dev->request, &snp_dev->secret_request,
+	       sizeof(snp_dev->secret_request));
+
 	rc = __handle_guest_request(snp_dev, exit_code, fw_err);
 	if (rc) {
 		if (rc == -EIO && *fw_err == SNP_GUEST_REQ_INVALID_LEN)
-- 
2.35.1

[PATCH -v3 11/11] x86/sev: Change snp_guest_issue_request()'s fw_err argument

[Borislav Petkov]

From: Dionna Glaze <dionnaglaze@google.com>

The GHCB specification declares that the firmware error value for
a guest request will be stored in the lower 32 bits of EXIT_INFO_2.  The
upper 32 bits are for the VMM's own error code. The fw_err argument to
snp_guest_issue_request() is thus a misnomer, and callers will need
access to all 64 bits.

The type of unsigned long also causes problems, since sw_exit_info2 is
u64 (unsigned long long) vs the argument's unsigned long*. Change this
type for issuing the guest request. Pass the ioctl command struct's error
field directly instead of in a local variable, since an incomplete guest
request may not set the error code, and uninitialized stack memory would
be written back to user space.

The firmware might not even be called, so bookend the call with the no
firmware call error and clear the error.

Since the "fw_err" field is really exitinfo2 split into the upper bits'
vmm error code and lower bits' firmware error code, convert the 64 bit
value to a union.

  [ bp:
   - Massage commit message
   - adjust code
   - Fix a build issue as
   Reported-by: kernel test robot <lkp@intel.com>
   Link: https://lore.kernel.org/oe-kbuild-all/202303070609.vX6wp2Af-lkp@intel.com
   - print exitinfo2 in hex
   Tom:
    - Correct -EIO exit case. ]

Signed-off-by: Dionna Glaze <dionnaglaze@google.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230214164638.1189804-5-dionnaglaze@google.com
---
 Documentation/virt/coco/sev-guest.rst   | 20 ++++---
 arch/x86/include/asm/sev-common.h       |  4 --
 arch/x86/include/asm/sev.h              | 10 ++--
 arch/x86/kernel/sev.c                   | 15 +++---
 drivers/virt/coco/sev-guest/sev-guest.c | 71 +++++++++++++------------
 include/uapi/linux/sev-guest.h          | 18 ++++++-
 6 files changed, 82 insertions(+), 56 deletions(-)

diff --git a/Documentation/virt/coco/sev-guest.rst b/Documentation/virt/coco/sev-guest.rst
index aa3e4c6a1f90..68b0d2363af8 100644
--- a/Documentation/virt/coco/sev-guest.rst
+++ b/Documentation/virt/coco/sev-guest.rst
@@ -37,11 +37,11 @@ along with a description:
       the return value.  General error numbers (-ENOMEM, -EINVAL)
       are not detailed, but errors with specific meanings are.
 
-The guest ioctl should be issued on a file descriptor of the /dev/sev-guest device.
-The ioctl accepts struct snp_user_guest_request. The input and output structure is
-specified through the req_data and resp_data field respectively. If the ioctl fails
-to execute due to a firmware error, then fw_err code will be set. Otherwise, fw_err
-will be set to 0x00000000ffffffff, i.e., the lower 32-bits are -1.
+The guest ioctl should be issued on a file descriptor of the /dev/sev-guest
+device.  The ioctl accepts struct snp_user_guest_request. The input and
+output structure is specified through the req_data and resp_data field
+respectively. If the ioctl fails to execute due to a firmware error, then
+the fw_error code will be set, otherwise fw_error will be set to -1.
 
 The firmware checks that the message sequence counter is one greater than
 the guests message sequence counter. If guest driver fails to increment message
@@ -57,8 +57,14 @@ counter (e.g. counter overflow), then -EIO will be returned.
                 __u64 req_data;
                 __u64 resp_data;
 
-                /* firmware error code on failure (see psp-sev.h) */
-                __u64 fw_err;
+                /* bits[63:32]: VMM error code, bits[31:0] firmware error code (see psp-sev.h) */
+                union {
+                        __u64 exitinfo2;
+                        struct {
+                                __u32 fw_error;
+                                __u32 vmm_error;
+                        };
+                };
         };
 
 2.1 SNP_GET_REPORT
diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
index b63be696b776..0759af9b1acf 100644
--- a/arch/x86/include/asm/sev-common.h
+++ b/arch/x86/include/asm/sev-common.h
@@ -128,10 +128,6 @@ struct snp_psc_desc {
 	struct psc_entry entries[VMGEXIT_PSC_MAX_ENTRY];
 } __packed;
 
-/* Guest message request error codes */
-#define SNP_GUEST_REQ_INVALID_LEN	BIT_ULL(32)
-#define SNP_GUEST_REQ_ERR_BUSY		BIT_ULL(33)
-
 #define GHCB_MSR_TERM_REQ		0x100
 #define GHCB_MSR_TERM_REASON_SET_POS	12
 #define GHCB_MSR_TERM_REASON_SET_MASK	0xf
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index ebc271bb6d8e..13dc2a9d23c1 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -9,6 +9,8 @@
 #define __ASM_ENCRYPTED_STATE_H
 
 #include <linux/types.h>
+#include <linux/sev-guest.h>
+
 #include <asm/insn.h>
 #include <asm/sev-common.h>
 #include <asm/bootparam.h>
@@ -185,6 +187,9 @@ static inline int pvalidate(unsigned long vaddr, bool rmp_psize, bool validate)
 
 	return rc;
 }
+
+struct snp_guest_request_ioctl;
+
 void setup_ghcb(void);
 void __init early_snp_set_memory_private(unsigned long vaddr, unsigned long paddr,
 					 unsigned int npages);
@@ -196,7 +201,7 @@ 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, struct snp_guest_request_ioctl *rio);
 #else
 static inline void sev_es_ist_enter(struct pt_regs *regs) { }
 static inline void sev_es_ist_exit(void) { }
@@ -216,8 +221,7 @@ 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, struct snp_guest_request_ioctl *rio)
 {
 	return -ENOTTY;
 }
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 3f664ab277c4..b031244d6d2d 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -22,6 +22,8 @@
 #include <linux/efi.h>
 #include <linux/platform_device.h>
 #include <linux/io.h>
+#include <linux/psp-sev.h>
+#include <uapi/linux/sev-guest.h>
 
 #include <asm/cpu_entry_area.h>
 #include <asm/stacktrace.h>
@@ -2175,7 +2177,7 @@ 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, struct snp_guest_request_ioctl *rio)
 {
 	struct ghcb_state state;
 	struct es_em_ctxt ctxt;
@@ -2183,8 +2185,7 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned
 	struct ghcb *ghcb;
 	int ret;
 
-	if (!fw_err)
-		return -EINVAL;
+	rio->exitinfo2 = SEV_RET_NO_FW_CALL;
 
 	/*
 	 * __sev_get_ghcb() needs to run with IRQs disabled because it is using
@@ -2209,16 +2210,16 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned
 	if (ret)
 		goto e_put;
 
-	*fw_err = ghcb->save.sw_exit_info_2;
-	switch (*fw_err) {
+	rio->exitinfo2 = ghcb->save.sw_exit_info_2;
+	switch (rio->exitinfo2) {
 	case 0:
 		break;
 
-	case SNP_GUEST_REQ_ERR_BUSY:
+	case SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_BUSY):
 		ret = -EAGAIN;
 		break;
 
-	case SNP_GUEST_REQ_INVALID_LEN:
+	case SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN):
 		/* Number of expected pages are returned in RBX */
 		if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST) {
 			input->data_npages = ghcb_get_rbx(ghcb);
diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 0c7b47acba2a..2764ede9b256 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -332,11 +332,12 @@ static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8
 	return __enc_payload(snp_dev, req, payload, sz);
 }
 
-static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, __u64 *fw_err)
+static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
+				  struct snp_guest_request_ioctl *rio)
 {
-	unsigned long err = 0xff, override_err = 0;
 	unsigned long req_start = jiffies;
 	unsigned int override_npages = 0;
+	u64 override_err = 0;
 	int rc;
 
 retry_request:
@@ -346,7 +347,7 @@ static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
 	 * sequence number must be incremented or the VMPCK must be deleted to
 	 * prevent reuse of the IV.
 	 */
-	rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
+	rc = snp_issue_guest_request(exit_code, &snp_dev->input, rio);
 	switch (rc) {
 	case -ENOSPC:
 		/*
@@ -364,7 +365,7 @@ static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
 		 * request buffer size was too small and give the caller the
 		 * required buffer size.
 		 */
-		override_err	= SNP_GUEST_REQ_INVALID_LEN;
+		override_err = SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN);
 
 		/*
 		 * If this call to the firmware succeeds, the sequence number can
@@ -377,7 +378,7 @@ static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
 		goto retry_request;
 
 	/*
-	 * The host may return SNP_GUEST_REQ_ERR_EBUSY if the request has been
+	 * The host may return SNP_GUEST_VMM_ERR_BUSY if the request has been
 	 * throttled. Retry in the driver to avoid returning and reusing the
 	 * message sequence number on a different message.
 	 */
@@ -398,27 +399,28 @@ static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
 	 */
 	snp_inc_msg_seqno(snp_dev);
 
-	if (fw_err)
-		*fw_err = override_err ?: err;
+	if (override_err) {
+		rio->exitinfo2 = override_err;
+
+		/* If an extended guest request was issued and the supplied certificate
+		 * buffer was not large enough, a standard guest request was issued to
+		 * prevent IV reuse. If the standard request was successful, return -EIO
+		 * back to the caller as would have originally been returned.
+		 */
+		if (!rc && override_err == SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN))
+			rc = -EIO;
+	}
 
 	if (override_npages)
 		snp_dev->input.data_npages = override_npages;
 
-	/*
-	 * If an extended guest request was issued and the supplied certificate
-	 * buffer was not large enough, a standard guest request was issued to
-	 * prevent IV reuse. If the standard request was successful, return -EIO
-	 * back to the caller as would have originally been returned.
-	 */
-	if (!rc && override_err == SNP_GUEST_REQ_INVALID_LEN)
-		return -EIO;
-
 	return rc;
 }
 
-static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
-				u8 type, void *req_buf, size_t req_sz, void *resp_buf,
-				u32 resp_sz, __u64 *fw_err)
+static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
+				struct snp_guest_request_ioctl *rio, u8 type,
+				void *req_buf, size_t req_sz, void *resp_buf,
+				u32 resp_sz)
 {
 	u64 seqno;
 	int rc;
@@ -432,7 +434,7 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 	memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
 
 	/* Encrypt the userspace provided payload in snp_dev->secret_request. */
-	rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
+	rc = enc_payload(snp_dev, seqno, rio->msg_version, type, req_buf, req_sz);
 	if (rc)
 		return rc;
 
@@ -443,12 +445,16 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 	memcpy(snp_dev->request, &snp_dev->secret_request,
 	       sizeof(snp_dev->secret_request));
 
-	rc = __handle_guest_request(snp_dev, exit_code, fw_err);
+	rc = __handle_guest_request(snp_dev, exit_code, rio);
 	if (rc) {
-		if (rc == -EIO && *fw_err == SNP_GUEST_REQ_INVALID_LEN)
+		if (rc == -EIO &&
+		    rio->exitinfo2 == SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN))
 			return rc;
 
-		dev_alert(snp_dev->dev, "Detected error from ASP request. rc: %d, fw_err: %llu\n", rc, *fw_err);
+		dev_alert(snp_dev->dev,
+			  "Detected error from ASP request. rc: %d, exitinfo2: 0x%llx\n",
+			  rc, rio->exitinfo2);
+
 		snp_disable_vmpck(snp_dev);
 		return rc;
 	}
@@ -488,9 +494,9 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
 	if (!resp)
 		return -ENOMEM;
 
-	rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg->msg_version,
+	rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg,
 				  SNP_MSG_REPORT_REQ, &req, sizeof(req), resp->data,
-				  resp_len, &arg->fw_err);
+				  resp_len);
 	if (rc)
 		goto e_free;
 
@@ -528,9 +534,8 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque
 	if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
 		return -EFAULT;
 
-	rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg->msg_version,
-				  SNP_MSG_KEY_REQ, &req, sizeof(req), buf, resp_len,
-				  &arg->fw_err);
+	rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg,
+				  SNP_MSG_KEY_REQ, &req, sizeof(req), buf, resp_len);
 	if (rc)
 		return rc;
 
@@ -590,12 +595,12 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
 		return -ENOMEM;
 
 	snp_dev->input.data_npages = npages;
-	ret = handle_guest_request(snp_dev, SVM_VMGEXIT_EXT_GUEST_REQUEST, arg->msg_version,
+	ret = handle_guest_request(snp_dev, SVM_VMGEXIT_EXT_GUEST_REQUEST, arg,
 				   SNP_MSG_REPORT_REQ, &req.data,
-				   sizeof(req.data), resp->data, resp_len, &arg->fw_err);
+				   sizeof(req.data), resp->data, resp_len);
 
 	/* If certs length is invalid then copy the returned length */
-	if (arg->fw_err == SNP_GUEST_REQ_INVALID_LEN) {
+	if (arg->vmm_error == SNP_GUEST_VMM_ERR_INVALID_LEN) {
 		req.certs_len = snp_dev->input.data_npages << PAGE_SHIFT;
 
 		if (copy_to_user((void __user *)arg->req_data, &req, sizeof(req)))
@@ -630,7 +635,7 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
 	if (copy_from_user(&input, argp, sizeof(input)))
 		return -EFAULT;
 
-	input.fw_err = 0xff;
+	input.exitinfo2 = 0xff;
 
 	/* Message version must be non-zero */
 	if (!input.msg_version)
@@ -661,7 +666,7 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
 
 	mutex_unlock(&snp_cmd_mutex);
 
-	if (input.fw_err && copy_to_user(argp, &input, sizeof(input)))
+	if (input.exitinfo2 && copy_to_user(argp, &input, sizeof(input)))
 		return -EFAULT;
 
 	return ret;
diff --git a/include/uapi/linux/sev-guest.h b/include/uapi/linux/sev-guest.h
index 256aaeff7e65..2aa39112cf8d 100644
--- a/include/uapi/linux/sev-guest.h
+++ b/include/uapi/linux/sev-guest.h
@@ -52,8 +52,14 @@ struct snp_guest_request_ioctl {
 	__u64 req_data;
 	__u64 resp_data;
 
-	/* firmware error code on failure (see psp-sev.h) */
-	__u64 fw_err;
+	/* bits[63:32]: VMM error code, bits[31:0] firmware error code (see psp-sev.h) */
+	union {
+		__u64 exitinfo2;
+		struct {
+			__u32 fw_error;
+			__u32 vmm_error;
+		};
+	};
 };
 
 struct snp_ext_report_req {
@@ -77,4 +83,12 @@ struct snp_ext_report_req {
 /* Get SNP extended report as defined in the GHCB specification version 2. */
 #define SNP_GET_EXT_REPORT _IOWR(SNP_GUEST_REQ_IOC_TYPE, 0x2, struct snp_guest_request_ioctl)
 
+/* Guest message request EXIT_INFO_2 constants */
+#define SNP_GUEST_FW_ERR_MASK		GENMASK_ULL(31, 0)
+#define SNP_GUEST_VMM_ERR_SHIFT		32
+#define SNP_GUEST_VMM_ERR(x)		(((u64)x) << SNP_GUEST_VMM_ERR_SHIFT)
+
+#define SNP_GUEST_VMM_ERR_INVALID_LEN	1
+#define SNP_GUEST_VMM_ERR_BUSY		2
+
 #endif /* __UAPI_LINUX_SEV_GUEST_H_ */
-- 
2.35.1

Re: [PATCH -v3 09/11] virt/coco/sev-guest: Add throttling awareness

[Dionna Amalie Glaze]

> @@ -320,7 +323,8 @@ static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8
>
>  static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, __u64 *fw_err)
>  {
> -       unsigned long err, override_err = 0;
> +       unsigned long err = 0xff, override_err = 0;
> +       unsigned long req_start = jiffies;
>         unsigned int override_npages = 0;
>         int rc;
>

Not blocking, but I do think in the previous version we discussed
changing this to the SEV_RET_NO_FW_CALL value instead of 0xff. I agree
that should be a later cleanup.

--
-Dionna Glaze, PhD (she/her)

Re: [PATCH -v3 00/11] SEV: Cleanup sev-guest a bit and add throttling

[Tom Lendacky]

On 3/7/23 13:24, Borislav Petkov wrote:
> From: "Borislav Petkov (AMD)" <bp@alien8.de>
> 
> From: "Borislav Petkov (AMD)" <bp@alien8.de>
> 
> Hi,
> 
> ok, here's v3, rebased ontop of -rc1 and hopefully with all the stuff
> addressed. There's always room for improvement but that should come
> later and ontop.
> 
> Thx.

For the series:
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

One thing I noticed is that patch #3 fixes an issue where the fw_err field 
returns uninitialized stack data when success (0) is returned by the 
ioctl(). There's no Fixes: tag on that commit. But I guess the later 
Fixes: tag on patch #9 would cause #3 to be pulled, too, right?

Thanks,
Tom

> 
> Changelog:
> ----------
> 
> v2:
> 
> ok, here's v2 with the pending stuff fixed.
> 
> Thx.
> 
> v1:
> ---
> so I've been looking at Dionna's patches adding the SEV guest throttling
> and that request issuing spaghetti was getting on my nerves. And it
> would've become even worse with more stuff piling ontop so here's
> a first round of cleanups before adding more stuff and making it an
> unmaintainable mess.
> 
> The final result is a lot easier to read with proper separation of
> functionality between functions. I want to get rid of more input/output
> params being passed back'n'forth and use a struct instead and Nikunj's
> patches have stuff which goes in that direction but first things first.
> 
> After the cleanup, the new stuff being added is a lot less code and
> almost trivial. But I've been staring at this for a while now so it
> could be only me who thinks it is trivial now. But we'll see.
> 
> Initial smoke testing seems to work ok but I might've introduced some
> funky bugs, ofc.
> 
> Comments and suggestions are appreciated, as always.
> 
> Thanks and thanks, Tom, for the help!
> 
> 
> Borislav Petkov (AMD) (7):
>    virt/coco/sev-guest: Check SEV_SNP attribute at probe time
>    virt/coco/sev-guest: Simplify extended guest request handling
>    virt/coco/sev-guest: Remove the disable_vmpck label in
>      handle_guest_request()
>    virt/coco/sev-guest: Carve out the request issuing logic into a helper
>    virt/coco/sev-guest: Do some code style cleanups
>    virt/coco/sev-guest: Convert the sw_exit_info_2 checking to a
>      switch-case
>    crypto: ccp: Get rid of __sev_platform_init_locked()'s local function
>      pointer
> 
> Dionna Glaze (3):
>    virt/coco/sev-guest: Add throttling awareness
>    virt/coco/sev-guest: Double-buffer messages
>    x86/sev: Change snp_guest_issue_request()'s fw_err argument
> 
> Peter Gonda (1):
>    crypto: ccp - Name -1 return value as SEV_RET_NO_FW_CALL
> 
>   Documentation/virt/coco/sev-guest.rst   |  20 ++-
>   arch/x86/include/asm/sev-common.h       |   3 -
>   arch/x86/include/asm/sev.h              |  10 +-
>   arch/x86/kernel/sev.c                   |  33 ++--
>   drivers/crypto/ccp/sev-dev.c            |  22 ++-
>   drivers/virt/coco/sev-guest/sev-guest.c | 190 +++++++++++++++---------
>   include/uapi/linux/psp-sev.h            |   7 +
>   include/uapi/linux/sev-guest.h          |  18 ++-
>   8 files changed, 199 insertions(+), 104 deletions(-)
> 

Re: [PATCH -v3 00/11] SEV: Cleanup sev-guest a bit and add throttling

[Borislav Petkov]

On Wed, Mar 08, 2023 at 02:33:58PM -0600, Tom Lendacky wrote:
> One thing I noticed is that patch #3 fixes an issue where the fw_err field
> returns uninitialized stack data when success (0) is returned by the
> ioctl(). There's no Fixes: tag on that commit. But I guess the later Fixes:
> tag on patch #9 would cause #3 to be pulled, too, right?

Yeah, that's the plan...

-- 
Regards/Gruss,
    Boris.

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