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SubjectRe: [PATCH 4.19 070/118] iommu/arm-smmu-v3: Dont disable SMMU in kdump kernel
Hi!

> [ Upstream commit 3f54c447df34ff9efac7809a4a80fd3208efc619 ]
>
> Disabling the SMMU when probing from within a kdump kernel so that all
> incoming transactions are terminated can prevent the core of the crashed
> kernel from being transferred off the machine if all I/O devices are
> behind the SMMU.
>
> Instead, continue to probe the SMMU after it is disabled so that we can
> reinitialise it entirely and re-attach the DMA masters as they are reset.
> Since the kdump kernel may not have drivers for all of the active DMA
> masters, we suppress fault reporting to avoid spamming the console and
> swamping the IRQ threads.

> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -2414,13 +2414,9 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu, bool bypass)
> /* Clear CR0 and sync (disables SMMU and queue processing) */
> reg = readl_relaxed(smmu->base + ARM_SMMU_CR0);
> if (reg & CR0_SMMUEN) {
> - if (is_kdump_kernel()) {
> - arm_smmu_update_gbpa(smmu, GBPA_ABORT, 0);
> - arm_smmu_device_disable(smmu);
> - return -EBUSY;
> - }
> -
> dev_warn(smmu->dev, "SMMU currently enabled! Resetting...\n");
> + WARN_ON(is_kdump_kernel() && !disable_bypass);
> + arm_smmu_update_gbpa(smmu, GBPA_ABORT, 0);
> }
>

This changes behaviour in !is_kdump_kernel() case. Is that
ok/intended?

Best regards,
Pavel

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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