[RESPIN PATCH] irqchip/gic-v4.1:Fix VSYNC referencing an unmapped VPE

[RESPIN PATCH] irqchip/gic-v4.1:Fix VSYNC referencing an unmapped VPE

[Nianyao Tang]

As per the GICv4.1 spec (Arm IHI 0069H, 5.3.19):

"A VMAPP with {V, Alloc}=={0, x} is self-synchronizing, This means the
ITS command queue does not show the command as consumed until all of
its effects are completed."

Furthermore, VSYNC is allowed to deliver an SError when referencing a
non existent VPE.

By these definitions, a VMAPP followed by a VSYNC is a bug, as the
later references a VPE that has been unmapped by the former.

Fix it by eliding the VSYNC in this scenario.

Fixes: 64edfaa9a234 ("irqchip/gic-v4.1: Implement the v4.1 flavour of VMAPP")

Signed-off-by: Nianyao Tang <tangnianyao@huawei.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
---
 drivers/irqchip/irq-gic-v3-its.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index fca888b36680..2a537cbfcb07 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -786,6 +786,7 @@ static struct its_vpe *its_build_vmapp_cmd(struct its_node *its,
 					   struct its_cmd_block *cmd,
 					   struct its_cmd_desc *desc)
 {
+	struct its_vpe *vpe = valid_vpe(its, desc->its_vmapp_cmd.vpe);
 	unsigned long vpt_addr, vconf_addr;
 	u64 target;
 	bool alloc;
@@ -798,6 +799,11 @@ static struct its_vpe *its_build_vmapp_cmd(struct its_node *its,
 		if (is_v4_1(its)) {
 			alloc = !atomic_dec_return(&desc->its_vmapp_cmd.vpe->vmapp_count);
 			its_encode_alloc(cmd, alloc);
+			/*
+			 * Unmapping a VPE is self-synchronizing on GICv4.1,
+			 * no need to issue a VSYNC.
+			 */
+			vpe = NULL;
 		}
 
 		goto out;
@@ -832,7 +838,7 @@ static struct its_vpe *its_build_vmapp_cmd(struct its_node *its,
 out:
 	its_fixup_cmd(cmd);
 
-	return valid_vpe(its, desc->its_vmapp_cmd.vpe);
+	return vpe;
 }
 
 static struct its_vpe *its_build_vmapti_cmd(struct its_node *its,
-- 
2.30.0


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Re: [RESPIN PATCH] irqchip/gic-v4.1:Fix VSYNC referencing an unmapped VPE

[Marc Zyngier]

On Sat, 06 Apr 2024 03:27:37 +0100,
Nianyao Tang <tangnianyao@huawei.com> wrote:
> 
> As per the GICv4.1 spec (Arm IHI 0069H, 5.3.19):
> 
> "A VMAPP with {V, Alloc}=={0, x} is self-synchronizing, This means the
> ITS command queue does not show the command as consumed until all of
> its effects are completed."
> 
> Furthermore, VSYNC is allowed to deliver an SError when referencing a
> non existent VPE.
> 
> By these definitions, a VMAPP followed by a VSYNC is a bug, as the
> later references a VPE that has been unmapped by the former.
> 
> Fix it by eliding the VSYNC in this scenario.
> 
> Fixes: 64edfaa9a234 ("irqchip/gic-v4.1: Implement the v4.1 flavour of VMAPP")
> 
> Signed-off-by: Nianyao Tang <tangnianyao@huawei.com>
> Reviewed-by: Marc Zyngier <maz@kernel.org>

Thanks for having taken my remarks into account, it looks good now.

Thomas, can you please take this as a fix for 6.9?

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

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Re: [RESPIN PATCH] irqchip/gic-v4.1:Fix VSYNC referencing an unmapped VPE

[Zenghui Yu]

On 2024/4/6 10:27, Nianyao Tang wrote:
> As per the GICv4.1 spec (Arm IHI 0069H, 5.3.19):
> 
> "A VMAPP with {V, Alloc}=={0, x} is self-synchronizing, This means the
> ITS command queue does not show the command as consumed until all of
> its effects are completed."
> 
> Furthermore, VSYNC is allowed to deliver an SError when referencing a
> non existent VPE.
> 
> By these definitions, a VMAPP followed by a VSYNC is a bug, as the
> later references a VPE that has been unmapped by the former.
> 
> Fix it by eliding the VSYNC in this scenario.
> 
> Fixes: 64edfaa9a234 ("irqchip/gic-v4.1: Implement the v4.1 flavour of VMAPP")
> 
> Signed-off-by: Nianyao Tang <tangnianyao@huawei.com>
> Reviewed-by: Marc Zyngier <maz@kernel.org>

Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>

Thanks.

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