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[124.171.83.152]) by smtp.gmail.com with ESMTPSA id d7sm15345413pfh.78.2020.06.22.18.11.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 22 Jun 2020 18:11:36 -0700 (PDT) Subject: Re: [PATCH 4/4] powerpc/pseries/iommu: Remove default DMA window before creating DDW To: Leonardo Bras , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Thiago Jung Bauermann , Ram Pai Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org References: <20200619050619.266888-1-leobras.c@gmail.com> <20200619050619.266888-5-leobras.c@gmail.com> <4bf1d32da3d13a44e3c2e4b04f369fe52c24a023.camel@gmail.com> From: Alexey Kardashevskiy Autocrypt: addr=aik@ozlabs.ru; keydata= mQINBE+rT0sBEADFEI2UtPRsLLvnRf+tI9nA8T91+jDK3NLkqV+2DKHkTGPP5qzDZpRSH6mD EePO1JqpVuIow/wGud9xaPA5uvuVgRS1q7RU8otD+7VLDFzPRiRE4Jfr2CW89Ox6BF+q5ZPV /pS4v4G9eOrw1v09lEKHB9WtiBVhhxKK1LnUjPEH3ifkOkgW7jFfoYgTdtB3XaXVgYnNPDFo PTBYsJy+wr89XfyHr2Ev7BB3Xaf7qICXdBF8MEVY8t/UFsesg4wFWOuzCfqxFmKEaPDZlTuR 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c7E5M+/NpslPCmYnDjs5qg0/3ihh6XuOGggZQOqrYPC3PnsNs3NxirwOkVPQgO6mXxpuifvJ DG9EMkK8IBXnLulqVk54kf7fE0jT/d8RTtJIA92GzsgdK2rpT1MBKKVffjRFGwN7nQVOzi4T XrB5p+6ML7Bd84xOEGsj/vdaXmz1esuH7BOZAGEZfLRCHJ0GVCSssg== Message-ID: Date: Tue, 23 Jun 2020 11:11:31 +1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <4bf1d32da3d13a44e3c2e4b04f369fe52c24a023.camel@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 23/06/2020 04:59, Leonardo Bras wrote: > Hello Alexey, thanks for the feedback! > > On Mon, 2020-06-22 at 20:02 +1000, Alexey Kardashevskiy wrote: >> >> On 19/06/2020 15:06, Leonardo Bras wrote: >>> On LoPAR "DMA Window Manipulation Calls", it's recommended to remove the >>> default DMA window for the device, before attempting to configure a DDW, >>> in order to make the maximum resources available for the next DDW to be >>> created. >>> >>> This is a requirement for some devices to use DDW, given they only >>> allow one DMA window. >>> >>> If setting up a new DDW fails anywhere after the removal of this >>> default DMA window, restore it using reset_dma_window. >> >> Nah... If we do it like this, then under pHyp we lose 32bit DMA for good >> as pHyp can only create a single window and it has to map at >> 0x800.0000.0000.0000. They probably do not care though. >> >> Under KVM, this will fail as VFIO allows creating 2 windows and it >> starts from 0 but the existing iommu_bypass_supported_pSeriesLP() treats >> the window address == 0 as a failure. And we want to keep both DMA >> windows for PCI adapters with both 64bit and 32bit PCI functions (I >> heard AMD GPU video + audio are like this) or someone could hotplug >> 32bit DMA device on a vphb with already present 64bit DMA window so we >> do not remove the default window. > > Well, then I would suggest doing something like this: > query_ddw(...); > if (query.windows_available == 0){ > remove_dma_window(...,default_win); > query_ddw(...); > } > > This would make sure to cover cases of windows available == 1 > and windows available > 1; Is "1" what pHyp returns on query? And was it always like that? Then it is probably ok. I just never really explored the idea of removing the default window as we did not have to. >> The last discussed thing I remember was that there was supposed to be a >> new bit in "ibm,architecture-vec-5" (forgot the details), we could use >> that to decide whether to keep the default window or not, like this. > > I checked on the latest LoPAR draft (soon to be published), for the > ibm,architecture-vec 'option array 5' and this entry was the only > recently added one that is related to this patchset: > > Byte 8 - Bit 0: > SRIOV Virtual Functions Support Dynamic DMA Windows (DDW): > 0: SRIOV Virtual Functions do not support DDW > 1: SRIOV Virtual Functions do support DDW > > Isn't this equivalent to having a "ibm,ddw-applicable" property? I am not sure, is there anything else to this new bit? I'd think if the client supports it, then pHyp will create one 64bit window per a PE and DDW API won't be needed. Thanks, > > >> >>> Signed-off-by: Leonardo Bras >>> --- >>> 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 de633f6ae093..68d1ea957ac7 100644 >>> --- a/arch/powerpc/platforms/pseries/iommu.c >>> +++ b/arch/powerpc/platforms/pseries/iommu.c >>> @@ -1074,8 +1074,9 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn) >>> u64 dma_addr, max_addr; >>> struct device_node *dn; >>> u32 ddw_avail[3]; >>> + >>> struct direct_window *window; >>> - struct property *win64; >>> + struct property *win64, *dfl_win; >> >> Make it "default_win" or "def_win", "dfl" hurts to read :) > > Sure, no problem :) > >> >>> struct dynamic_dma_window_prop *ddwprop; >>> struct failed_ddw_pdn *fpdn; >>> >>> @@ -1110,8 +1111,19 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn) >>> if (ret) >>> goto out_failed; >>> >>> - /* >>> - * Query if there is a second window of size to map the >>> + /* >>> + * First step of setting up DDW is removing the default DMA window, >>> + * if it's present. It will make all the resources available to the >>> + * new DDW window. >>> + * If anything fails after this, we need to restore it. >>> + */ >>> + >>> + dfl_win = of_find_property(pdn, "ibm,dma-window", NULL); >>> + if (dfl_win) >>> + remove_dma_window(pdn, ddw_avail, dfl_win); >> >> Before doing so, you want to make sure that the "reset" is actually >> supported. Thanks, > > Good catch, I will improve that. > >> >> >>> + >>> + /* >>> + * Query if there is a window of size to map the >>> * whole partition. Query returns number of windows, largest >>> * block assigned to PE (partition endpoint), and two bitmasks >>> * of page sizes: supported and supported for migrate-dma. >>> @@ -1219,6 +1231,8 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn) >>> kfree(win64); >>> >>> out_failed: >>> + if (dfl_win) >>> + reset_dma_window(dev, pdn); >>> >>> fpdn = kzalloc(sizeof(*fpdn), GFP_KERNEL); >>> if (!fpdn) >>> > > Best regards, > Leonardo > -- Alexey