* [PATCH] iommu/amd: Don't put completion-wait semaphore on stack @ 2016-09-14 9:41 Joerg Roedel [not found] ` <1473846119-9527-1-git-send-email-joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org> 0 siblings, 1 reply; 7+ messages in thread From: Joerg Roedel @ 2016-09-14 9:41 UTC (permalink / raw) To: Ingo Molnar, hpa-YMNOUZJC4hwAvxtiuMwx3w, tglx-hfZtesqFncYOwBW4kG4KsQ Cc: Joerg Roedel, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA, x86-DgEjT+Ai2ygdnm+yROfE0A, bp-Gina5bIWoIWzQB+pC5nmwQ, Andy Lutomirski From: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org> The semaphore used by the AMD IOMMU to signal command completion lived on the stack until now, which was safe as the driver busy-waited on the semaphore with IRQs disabled, so the stack can't go away under the driver. But the recently introduced vmap-based stacks break this as the physical address of the semaphore can't be determinded easily anymore. The driver used the __pa() macro, but that only works in the direct-mapping. The result were Completion-Wait timeout errors seen by the IOMMU driver, breaking system boot. Since putting the semaphore on the stack is bad design anyway, move the semaphore into 'struct amd_iommu'. It is protected by the per-iommu lock and now in the direct mapping again. This fixes the Completion-Wait timeout errors and makes AMD IOMMU systems boot again with vmap-based stacks enabled. Reported-by: Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org> Signed-off-by: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org> --- drivers/iommu/amd_iommu.c | 14 ++++++++------ drivers/iommu/amd_iommu_types.h | 2 ++ 2 files changed, 10 insertions(+), 6 deletions(-) diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c index 96de97a..1307e73 100644 --- a/drivers/iommu/amd_iommu.c +++ b/drivers/iommu/amd_iommu.c @@ -957,15 +957,16 @@ again: if (left <= 2) { struct iommu_cmd sync_cmd; - volatile u64 sem = 0; int ret; - build_completion_wait(&sync_cmd, (u64)&sem); + iommu->cmd_sem = 0; + + build_completion_wait(&sync_cmd, (u64)&iommu->cmd_sem); copy_cmd_to_buffer(iommu, &sync_cmd, tail); spin_unlock_irqrestore(&iommu->lock, flags); - if ((ret = wait_on_sem(&sem)) != 0) + if ((ret = wait_on_sem(&iommu->cmd_sem)) != 0) return ret; goto again; @@ -993,19 +994,20 @@ static int iommu_queue_command(struct amd_iommu *iommu, struct iommu_cmd *cmd) static int iommu_completion_wait(struct amd_iommu *iommu) { struct iommu_cmd cmd; - volatile u64 sem = 0; int ret; if (!iommu->need_sync) return 0; - build_completion_wait(&cmd, (u64)&sem); + iommu->cmd_sem = 0; + + build_completion_wait(&cmd, (u64)&iommu->cmd_sem); ret = iommu_queue_command_sync(iommu, &cmd, false); if (ret) return ret; - return wait_on_sem(&sem); + return wait_on_sem(&iommu->cmd_sem); } static int iommu_flush_dte(struct amd_iommu *iommu, u16 devid) diff --git a/drivers/iommu/amd_iommu_types.h b/drivers/iommu/amd_iommu_types.h index caf5e38..9652848 100644 --- a/drivers/iommu/amd_iommu_types.h +++ b/drivers/iommu/amd_iommu_types.h @@ -524,6 +524,8 @@ struct amd_iommu { struct irq_domain *ir_domain; struct irq_domain *msi_domain; #endif + + volatile u64 __aligned(8) cmd_sem; }; #define ACPIHID_UID_LEN 256 -- 2.6.2 ^ permalink raw reply related [flat|nested] 7+ messages in thread
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* Re: [PATCH] iommu/amd: Don't put completion-wait semaphore on stack [not found] ` <1473846119-9527-1-git-send-email-joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org> @ 2016-09-14 15:26 ` Ingo Molnar [not found] ` <20160914152647.GA13814-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 0 siblings, 1 reply; 7+ messages in thread From: Ingo Molnar @ 2016-09-14 15:26 UTC (permalink / raw) To: Joerg Roedel Cc: Joerg Roedel, x86-DgEjT+Ai2ygdnm+yROfE0A, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA, Ingo Molnar, bp-Gina5bIWoIWzQB+pC5nmwQ, Andy Lutomirski, hpa-YMNOUZJC4hwAvxtiuMwx3w, tglx-hfZtesqFncYOwBW4kG4KsQ * Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org> wrote: > From: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org> > > The semaphore used by the AMD IOMMU to signal command > completion lived on the stack until now, which was safe as > the driver busy-waited on the semaphore with IRQs disabled, > so the stack can't go away under the driver. > > But the recently introduced vmap-based stacks break this as > the physical address of the semaphore can't be determinded > easily anymore. The driver used the __pa() macro, but that > only works in the direct-mapping. The result were > Completion-Wait timeout errors seen by the IOMMU driver, > breaking system boot. > > Since putting the semaphore on the stack is bad design > anyway, move the semaphore into 'struct amd_iommu'. It is > protected by the per-iommu lock and now in the direct > mapping again. This fixes the Completion-Wait timeout errors > and makes AMD IOMMU systems boot again with vmap-based > stacks enabled. > > Reported-by: Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org> > Signed-off-by: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org> > --- > drivers/iommu/amd_iommu.c | 14 ++++++++------ > drivers/iommu/amd_iommu_types.h | 2 ++ > 2 files changed, 10 insertions(+), 6 deletions(-) Cool, thanks! I'll put this into tip:x86/asm which has the virtually mapped stack patches - ok? Thanks, Ingo ^ permalink raw reply [flat|nested] 7+ messages in thread
[parent not found: <20160914152647.GA13814-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]
* Re: [PATCH] iommu/amd: Don't put completion-wait semaphore on stack [not found] ` <20160914152647.GA13814-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> @ 2016-09-14 21:27 ` Joerg Roedel [not found] ` <20160914212712.GD1437-zLv9SwRftAIdnm+yROfE0A@public.gmane.org> 0 siblings, 1 reply; 7+ messages in thread From: Joerg Roedel @ 2016-09-14 21:27 UTC (permalink / raw) To: Ingo Molnar Cc: Joerg Roedel, x86-DgEjT+Ai2ygdnm+yROfE0A, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA, Ingo Molnar, bp-Gina5bIWoIWzQB+pC5nmwQ, Andy Lutomirski, hpa-YMNOUZJC4hwAvxtiuMwx3w, tglx-hfZtesqFncYOwBW4kG4KsQ Hi Ingo, On Wed, Sep 14, 2016 at 05:26:48PM +0200, Ingo Molnar wrote: > > Cool, thanks! I'll put this into tip:x86/asm which has the virtually mapped stack > patches - ok? Yeah, sure, that is the best thing to do. Just wait for the v2 I'll sending tomorrow. I just realised that the locking is not correct in one of the cases with this patch and I'd like to fix that first. Thanks, Joerg ^ permalink raw reply [flat|nested] 7+ messages in thread
[parent not found: <20160914212712.GD1437-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>]
* Re: [PATCH] iommu/amd: Don't put completion-wait semaphore on stack [not found] ` <20160914212712.GD1437-zLv9SwRftAIdnm+yROfE0A@public.gmane.org> @ 2016-09-14 21:38 ` Joerg Roedel [not found] ` <20160914213835.GA28800-l3A5Bk7waGM@public.gmane.org> 0 siblings, 1 reply; 7+ messages in thread From: Joerg Roedel @ 2016-09-14 21:38 UTC (permalink / raw) To: Joerg Roedel Cc: x86-DgEjT+Ai2ygdnm+yROfE0A, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA, Ingo Molnar, bp-Gina5bIWoIWzQB+pC5nmwQ, Andy Lutomirski, hpa-YMNOUZJC4hwAvxtiuMwx3w, tglx-hfZtesqFncYOwBW4kG4KsQ, Ingo Molnar On Wed, Sep 14, 2016 at 11:27:12PM +0200, Joerg Roedel wrote: > On Wed, Sep 14, 2016 at 05:26:48PM +0200, Ingo Molnar wrote: > > > > Cool, thanks! I'll put this into tip:x86/asm which has the virtually mapped stack > > patches - ok? > > Yeah, sure, that is the best thing to do. Just wait for the v2 I'll > sending tomorrow. I just realised that the locking is not correct in one > of the cases with this patch and I'd like to fix that first. Oh sorry, just saw the tip-bot mail. Let me know whether you can still remove it and just take v2 or if you want a follow-on patch. Thanks, Joerg ^ permalink raw reply [flat|nested] 7+ messages in thread
[parent not found: <20160914213835.GA28800-l3A5Bk7waGM@public.gmane.org>]
* Re: [PATCH] iommu/amd: Don't put completion-wait semaphore on stack [not found] ` <20160914213835.GA28800-l3A5Bk7waGM@public.gmane.org> @ 2016-09-15 5:44 ` Ingo Molnar [not found] ` <20160915054435.GA25155-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 0 siblings, 1 reply; 7+ messages in thread From: Ingo Molnar @ 2016-09-15 5:44 UTC (permalink / raw) To: Joerg Roedel Cc: x86-DgEjT+Ai2ygdnm+yROfE0A, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA, Ingo Molnar, bp-Gina5bIWoIWzQB+pC5nmwQ, Andy Lutomirski, hpa-YMNOUZJC4hwAvxtiuMwx3w, tglx-hfZtesqFncYOwBW4kG4KsQ * Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org> wrote: > On Wed, Sep 14, 2016 at 11:27:12PM +0200, Joerg Roedel wrote: > > On Wed, Sep 14, 2016 at 05:26:48PM +0200, Ingo Molnar wrote: > > > > > > Cool, thanks! I'll put this into tip:x86/asm which has the virtually mapped stack > > > patches - ok? > > > > Yeah, sure, that is the best thing to do. Just wait for the v2 I'll > > sending tomorrow. I just realised that the locking is not correct in one > > of the cases with this patch and I'd like to fix that first. > > Oh sorry, just saw the tip-bot mail. Let me know whether you can still > remove it and just take v2 or if you want a follow-on patch. Yeah, I can still remove it - just zapped it in fact. Thanks, Ingo ^ permalink raw reply [flat|nested] 7+ messages in thread
[parent not found: <20160915054435.GA25155-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]
* [PATCH v2] iommu/amd: Don't put completion-wait semaphore on stack [not found] ` <20160915054435.GA25155-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> @ 2016-09-15 8:29 ` Joerg Roedel [not found] ` <20160915082931.GF1437-zLv9SwRftAIdnm+yROfE0A@public.gmane.org> 0 siblings, 1 reply; 7+ messages in thread From: Joerg Roedel @ 2016-09-15 8:29 UTC (permalink / raw) To: Ingo Molnar Cc: Joerg Roedel, x86-DgEjT+Ai2ygdnm+yROfE0A, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA, Ingo Molnar, bp-Gina5bIWoIWzQB+pC5nmwQ, Andy Lutomirski, hpa-YMNOUZJC4hwAvxtiuMwx3w, tglx-hfZtesqFncYOwBW4kG4KsQ Hi Ingo, On Thu, Sep 15, 2016 at 07:44:35AM +0200, Ingo Molnar wrote: > Yeah, I can still remove it - just zapped it in fact. Thanks, and sorry for the hassle. Here is the v2 patch that has the correct locking. I tested it with and without lockdep enabled and also under some load. Looks all fine. So here is the patch: >From 9becedb853c682c3fc3dd5574b933df216d91acd Mon Sep 17 00:00:00 2001 From: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org> Date: Wed, 14 Sep 2016 11:41:59 +0200 Subject: [PATCH] iommu/amd: Don't put completion-wait semaphore on stack The semaphore used by the AMD IOMMU to signal command completion lived on the stack until now, which was safe as the driver busy-waited on the semaphore with IRQs disabled, so the stack can't go away under the driver. But the recently introduced vmap-based stacks break this as the physical address of the semaphore can't be determinded easily anymore. The driver used the __pa() macro, but that only works in the direct-mapping. The result were Completion-Wait timeout errors seen by the IOMMU driver, breaking system boot. Since putting the semaphore on the stack is bad design anyway, move the semaphore into 'struct amd_iommu'. It is protected by the per-iommu lock and now in the direct mapping again. This fixes the Completion-Wait timeout errors and makes AMD IOMMU systems boot again with vmap-based stacks enabled. Reported-by: Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org> Signed-off-by: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org> --- drivers/iommu/amd_iommu.c | 51 ++++++++++++++++++++++++++++------------- drivers/iommu/amd_iommu_types.h | 2 ++ 2 files changed, 37 insertions(+), 16 deletions(-) diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c index 96de97a..4025291 100644 --- a/drivers/iommu/amd_iommu.c +++ b/drivers/iommu/amd_iommu.c @@ -940,15 +940,13 @@ static void build_inv_irt(struct iommu_cmd *cmd, u16 devid) * Writes the command to the IOMMUs command buffer and informs the * hardware about the new command. */ -static int iommu_queue_command_sync(struct amd_iommu *iommu, - struct iommu_cmd *cmd, - bool sync) +static int __iommu_queue_command_sync(struct amd_iommu *iommu, + struct iommu_cmd *cmd, + bool sync) { u32 left, tail, head, next_tail; - unsigned long flags; again: - spin_lock_irqsave(&iommu->lock, flags); head = readl(iommu->mmio_base + MMIO_CMD_HEAD_OFFSET); tail = readl(iommu->mmio_base + MMIO_CMD_TAIL_OFFSET); @@ -957,15 +955,14 @@ again: if (left <= 2) { struct iommu_cmd sync_cmd; - volatile u64 sem = 0; int ret; - build_completion_wait(&sync_cmd, (u64)&sem); - copy_cmd_to_buffer(iommu, &sync_cmd, tail); + iommu->cmd_sem = 0; - spin_unlock_irqrestore(&iommu->lock, flags); + build_completion_wait(&sync_cmd, (u64)&iommu->cmd_sem); + copy_cmd_to_buffer(iommu, &sync_cmd, tail); - if ((ret = wait_on_sem(&sem)) != 0) + if ((ret = wait_on_sem(&iommu->cmd_sem)) != 0) return ret; goto again; @@ -976,9 +973,21 @@ again: /* We need to sync now to make sure all commands are processed */ iommu->need_sync = sync; + return 0; +} + +static int iommu_queue_command_sync(struct amd_iommu *iommu, + struct iommu_cmd *cmd, + bool sync) +{ + unsigned long flags; + int ret; + + spin_lock_irqsave(&iommu->lock, flags); + ret = __iommu_queue_command_sync(iommu, cmd, sync); spin_unlock_irqrestore(&iommu->lock, flags); - return 0; + return ret; } static int iommu_queue_command(struct amd_iommu *iommu, struct iommu_cmd *cmd) @@ -993,19 +1002,29 @@ static int iommu_queue_command(struct amd_iommu *iommu, struct iommu_cmd *cmd) static int iommu_completion_wait(struct amd_iommu *iommu) { struct iommu_cmd cmd; - volatile u64 sem = 0; + unsigned long flags; int ret; if (!iommu->need_sync) return 0; - build_completion_wait(&cmd, (u64)&sem); - ret = iommu_queue_command_sync(iommu, &cmd, false); + build_completion_wait(&cmd, (u64)&iommu->cmd_sem); + + spin_lock_irqsave(&iommu->lock, flags); + + iommu->cmd_sem = 0; + + ret = __iommu_queue_command_sync(iommu, &cmd, false); if (ret) - return ret; + goto out_unlock; + + ret = wait_on_sem(&iommu->cmd_sem); - return wait_on_sem(&sem); +out_unlock: + spin_unlock_irqrestore(&iommu->lock, flags); + + return ret; } static int iommu_flush_dte(struct amd_iommu *iommu, u16 devid) diff --git a/drivers/iommu/amd_iommu_types.h b/drivers/iommu/amd_iommu_types.h index caf5e38..9652848 100644 --- a/drivers/iommu/amd_iommu_types.h +++ b/drivers/iommu/amd_iommu_types.h @@ -524,6 +524,8 @@ struct amd_iommu { struct irq_domain *ir_domain; struct irq_domain *msi_domain; #endif + + volatile u64 __aligned(8) cmd_sem; }; #define ACPIHID_UID_LEN 256 -- 2.6.2 ^ permalink raw reply related [flat|nested] 7+ messages in thread
[parent not found: <20160915082931.GF1437-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>]
* Re: [PATCH v2] iommu/amd: Don't put completion-wait semaphore on stack [not found] ` <20160915082931.GF1437-zLv9SwRftAIdnm+yROfE0A@public.gmane.org> @ 2016-09-15 9:28 ` Ingo Molnar 0 siblings, 0 replies; 7+ messages in thread From: Ingo Molnar @ 2016-09-15 9:28 UTC (permalink / raw) To: Joerg Roedel Cc: Joerg Roedel, x86-DgEjT+Ai2ygdnm+yROfE0A, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA, Ingo Molnar, bp-Gina5bIWoIWzQB+pC5nmwQ, Andy Lutomirski, hpa-YMNOUZJC4hwAvxtiuMwx3w, tglx-hfZtesqFncYOwBW4kG4KsQ * Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org> wrote: > Hi Ingo, > > On Thu, Sep 15, 2016 at 07:44:35AM +0200, Ingo Molnar wrote: > > Yeah, I can still remove it - just zapped it in fact. > > Thanks, and sorry for the hassle. Here is the v2 patch that has the > correct locking. I tested it with and without lockdep enabled and also > under some load. Looks all fine. Thanks a lot for the quick response! Ingo ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2016-09-15 9:28 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2016-09-14 9:41 [PATCH] iommu/amd: Don't put completion-wait semaphore on stack Joerg Roedel [not found] ` <1473846119-9527-1-git-send-email-joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org> 2016-09-14 15:26 ` Ingo Molnar [not found] ` <20160914152647.GA13814-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 2016-09-14 21:27 ` Joerg Roedel [not found] ` <20160914212712.GD1437-zLv9SwRftAIdnm+yROfE0A@public.gmane.org> 2016-09-14 21:38 ` Joerg Roedel [not found] ` <20160914213835.GA28800-l3A5Bk7waGM@public.gmane.org> 2016-09-15 5:44 ` Ingo Molnar [not found] ` <20160915054435.GA25155-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 2016-09-15 8:29 ` [PATCH v2] " Joerg Roedel [not found] ` <20160915082931.GF1437-zLv9SwRftAIdnm+yROfE0A@public.gmane.org> 2016-09-15 9:28 ` Ingo Molnar
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