From: Alexey Kardashevskiy <aik@ozlabs.ru>
To: Ram Pai <linuxram@us.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org, benh@kernel.crashing.org,
david@gibson.dropbear.id.au, mpe@ellerman.id.au,
paulus@ozlabs.org, mdroth@linux.vnet.ibm.com, hch@lst.de,
andmike@us.ibm.com, sukadev@linux.vnet.ibm.com, mst@redhat.com,
ram.n.pai@gmail.com, cai@lca.pw, tglx@linutronix.de,
bauerman@linux.ibm.com, linux-kernel@vger.kernel.org
Subject: Re: [RFC v1 1/2] powerpc/pseries/iommu: Share the per-cpu TCE page with the hypervisor.
Date: Thu, 7 Nov 2019 16:58:55 +1100 [thread overview]
Message-ID: <6c367fc2-03f5-3ea4-3cd7-9c4af1df1d4c@ozlabs.ru> (raw)
In-Reply-To: <20191106170153.GC5201@oc0525413822.ibm.com>
On 07/11/2019 04:01, Ram Pai wrote:
> On Wed, Nov 06, 2019 at 12:58:50PM +1100, Alexey Kardashevskiy wrote:
>>
>>
>> On 05/11/2019 08:28, Ram Pai wrote:
>>> The hypervisor needs to access the contents of the page holding the TCE
>>> entries while setting up the TCE entries in the IOMMU's TCE table. For
>>> SecureVMs, since this page is encrypted, the hypervisor cannot access
>>> valid entries. Share the page with the hypervisor. This ensures that the
>>> hypervisor sees the valid entries.
>>>
>>> Signed-off-by: Ram Pai <linuxram@us.ibm.com>
>>> ---
>>> arch/powerpc/platforms/pseries/iommu.c | 20 +++++++++++++++++---
>>> 1 file changed, 17 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
>>> index 8d9c2b1..07f0847 100644
>>> --- a/arch/powerpc/platforms/pseries/iommu.c
>>> +++ b/arch/powerpc/platforms/pseries/iommu.c
>>> @@ -37,6 +37,7 @@
>>> #include <asm/mmzone.h>
>>> #include <asm/plpar_wrappers.h>
>>> #include <asm/svm.h>
>>> +#include <asm/ultravisor.h>
>>>
>>> #include "pseries.h"
>>>
>>> @@ -179,6 +180,19 @@ static int tce_build_pSeriesLP(struct iommu_table *tbl, long tcenum,
>>>
>>> static DEFINE_PER_CPU(__be64 *, tce_page);
>>>
>>> +/*
>>> + * Allocate a tce page. If secure VM, share the page with the hypervisor.
>>> + */
>>> +static __be64 *alloc_tce_page(void)
>>> +{
>>> + __be64 *tcep = (__be64 *)__get_free_page(GFP_ATOMIC);
>>> +
>>> + if (tcep && is_secure_guest())
>>> + uv_share_page(PHYS_PFN(__pa(tcep)), 1);
>>
>>
>> There is no matching unshare in this patch.
>
> The page is allocated and shared, and stays that way for the life of the
> kernel. It is not explicitly unshared or freed.
Ah, fair enough, I missed that, strange that we do not free it but ok. Thanks,
> It is however
> implicitly unshared by the guest kernel, through a UV_UNSHARE_ALL_PAGES ucall
> when the guest kernel reboots. And it also gets implicitly unshared by
> the Ultravisor/Hypervisor, if the SVM abruptly terminates.
>
>>
>>
>>> +
>>> + return tcep;
>>> +}
>>> +
>>> static int tce_buildmulti_pSeriesLP(struct iommu_table *tbl, long tcenum,
>>> long npages, unsigned long uaddr,
>>> enum dma_data_direction direction,
>>> @@ -206,8 +220,7 @@ static int tce_buildmulti_pSeriesLP(struct iommu_table *tbl, long tcenum,
>>> * from iommu_alloc{,_sg}()
>>> */
>>> if (!tcep) {
>>> - tcep = (__be64 *)__get_free_page(GFP_ATOMIC);
>>> - /* If allocation fails, fall back to the loop implementation */
>>> + tcep = alloc_tce_page();
>>> if (!tcep) {
>>> local_irq_restore(flags);
>>> return tce_build_pSeriesLP(tbl, tcenum, npages, uaddr,
>>> @@ -391,6 +404,7 @@ static int tce_clearrange_multi_pSeriesLP(unsigned long start_pfn,
>>> return rc;
>>> }
>>>
>>> +
>>
>> Unrelated.
>
> yes. will fix it.
>
> Thanks,
> RP
>
--
Alexey
next prev parent reply other threads:[~2019-11-07 5:59 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-04 21:28 [RFC v1 0/2] Enable IOMMU support for pseries Secure VMs Ram Pai
2019-11-04 21:28 ` [RFC v1 1/2] powerpc/pseries/iommu: Share the per-cpu TCE page with the hypervisor Ram Pai
2019-11-04 21:28 ` [RFC v1 2/2] powerpc/pseries/iommu: Use dma_iommu_ops for Secure VMs aswell Ram Pai
2019-11-07 10:26 ` Michael Ellerman
2019-11-08 5:49 ` Ram Pai
2019-11-06 1:58 ` [RFC v1 1/2] powerpc/pseries/iommu: Share the per-cpu TCE page with the hypervisor Alexey Kardashevskiy
2019-11-06 17:01 ` Ram Pai
2019-11-07 5:58 ` Alexey Kardashevskiy [this message]
2019-11-07 10:29 ` Michael Ellerman
2019-11-08 6:05 ` Ram Pai
2019-11-06 1:59 ` [RFC v1 0/2] Enable IOMMU support for pseries Secure VMs Alexey Kardashevskiy
2019-11-06 16:46 ` Ram Pai
2019-11-06 18:06 ` Michael S. Tsirkin
2019-11-06 18:52 ` Michael Roth
2019-11-06 22:22 ` Ram Pai
2019-11-07 6:01 ` Alexey Kardashevskiy
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