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From: Robin Murphy <robin.murphy@arm.com>
To: Ross Philipson <ross.philipson@oracle.com>,
	linux-kernel@vger.kernel.org, x86@kernel.org,
	iommu@lists.linux-foundation.org,
	linux-integrity@vger.kernel.org, linux-doc@vger.kernel.org
Cc: dpsmith@apertussolutions.com, luto@amacapital.net,
	mingo@redhat.com, bp@alien8.de, hpa@zytor.com,
	tglx@linutronix.de, trenchboot-devel@googlegroups.com
Subject: Re: [PATCH v2 12/12] iommu: Do not allow IOMMU passthrough with Secure Launch
Date: Fri, 18 Jun 2021 19:32:27 +0100	[thread overview]
Message-ID: <53edcf0e-c094-876c-ac3d-7c9752e9ea99@arm.com> (raw)
In-Reply-To: <1624032777-7013-13-git-send-email-ross.philipson@oracle.com>

On 2021-06-18 17:12, Ross Philipson wrote:
> The IOMMU should always be set to default translated type after
> the PMRs are disabled to protect the MLE from DMA.
> 
> Signed-off-by: Ross Philipson <ross.philipson@oracle.com>
> ---
>   drivers/iommu/intel/iommu.c | 5 +++++
>   drivers/iommu/iommu.c       | 6 +++++-
>   2 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index be35284..4f0256d 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -41,6 +41,7 @@
>   #include <linux/dma-direct.h>
>   #include <linux/crash_dump.h>
>   #include <linux/numa.h>
> +#include <linux/slaunch.h>
>   #include <asm/irq_remapping.h>
>   #include <asm/cacheflush.h>
>   #include <asm/iommu.h>
> @@ -2877,6 +2878,10 @@ static bool device_is_rmrr_locked(struct device *dev)
>    */
>   static int device_def_domain_type(struct device *dev)
>   {
> +	/* Do not allow identity domain when Secure Launch is configured */
> +	if (slaunch_get_flags() & SL_FLAG_ACTIVE)
> +		return IOMMU_DOMAIN_DMA;

Is this specific to Intel? It seems like it could easily be done 
commonly like the check for untrusted external devices.

> +
>   	if (dev_is_pci(dev)) {
>   		struct pci_dev *pdev = to_pci_dev(dev);
>   
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 808ab70d..d49b7dd 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -23,6 +23,7 @@
>   #include <linux/property.h>
>   #include <linux/fsl/mc.h>
>   #include <linux/module.h>
> +#include <linux/slaunch.h>
>   #include <trace/events/iommu.h>
>   
>   static struct kset *iommu_group_kset;
> @@ -2761,7 +2762,10 @@ void iommu_set_default_passthrough(bool cmd_line)
>   {
>   	if (cmd_line)
>   		iommu_cmd_line |= IOMMU_CMD_LINE_DMA_API;
> -	iommu_def_domain_type = IOMMU_DOMAIN_IDENTITY;
> +
> +	/* Do not allow identity domain when Secure Launch is configured */
> +	if (!(slaunch_get_flags() & SL_FLAG_ACTIVE))
> +		iommu_def_domain_type = IOMMU_DOMAIN_IDENTITY;

Quietly ignoring the setting and possibly leaving iommu_def_domain_type 
uninitialised (note that 0 is not actually a usable type) doesn't seem 
great. AFAICS this probably warrants similar treatment to the 
mem_encrypt_active() case - there doesn't seem a great deal of value in 
trying to save users from themselves if they care about measured boot 
yet explicitly pass options which may compromise measured boot. If you 
really want to go down that route there's at least the sysfs interface 
you'd need to nobble as well, not to mention the various ways of 
completely disabling IOMMUs...

It might be reasonable to make IOMMU_DEFAULT_PASSTHROUGH depend on 
!SECURE_LAUNCH for clarity though.

Robin.

>   }
>   
>   void iommu_set_default_translated(bool cmd_line)
> 

  reply	other threads:[~2021-06-18 18:32 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-18 16:12 [PATCH v2 00/12] x86: Trenchboot secure dynamic launch Linux kernel support Ross Philipson
2021-06-18 16:12 ` [PATCH v2 01/12] x86/boot: Place kernel_info at a fixed offset Ross Philipson
2021-06-18 16:12 ` [PATCH v2 02/12] x86: Secure Launch Kconfig Ross Philipson
2021-06-18 16:12 ` [PATCH v2 03/12] x86: Secure Launch main header file Ross Philipson
2021-06-18 16:12 ` [PATCH v2 04/12] x86: Add early SHA support for Secure Launch early measurements Ross Philipson
2021-06-18 16:12 ` [PATCH v2 05/12] x86: Secure Launch kernel early boot stub Ross Philipson
2021-06-18 16:12 ` [PATCH v2 06/12] x86: Secure Launch kernel late " Ross Philipson
2021-06-18 16:12 ` [PATCH v2 07/12] x86: Secure Launch SMP bringup support Ross Philipson
2021-06-18 16:12 ` [PATCH v2 08/12] kexec: Secure Launch kexec SEXIT support Ross Philipson
2021-06-18 16:12 ` [PATCH v2 09/12] reboot: Secure Launch SEXIT support on reboot paths Ross Philipson
2021-06-18 16:12 ` [PATCH v2 10/12] x86: Secure Launch late initcall platform module Ross Philipson
2021-06-18 16:12 ` [PATCH v2 11/12] tpm: Allow locality 2 to be set when initializing the TPM for Secure Launch Ross Philipson
2021-06-18 16:12 ` [PATCH v2 12/12] iommu: Do not allow IOMMU passthrough with " Ross Philipson
2021-06-18 18:32   ` Robin Murphy [this message]
2021-06-21 17:51     ` Ross Philipson
2021-06-21 21:15       ` Andy Lutomirski
2021-06-30  9:50         ` Ross Philipson
2021-08-04  3:05         ` Daniel P. Smith
2021-06-22 11:06       ` Robin Murphy
2021-06-30  9:47         ` Ross Philipson

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