* [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
* 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
* 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
* 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
* 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
* [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
* 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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