Get physical addresses from a user-mode pointer
in [Device Drivers]
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From: Olivier on 20 Jan 2009 07:56 Hello, Within a driver, is there a way to recover the physical addresses of memory pages that are behind a user-mode buffer pointer given via an IOCTL, as an example? Thanks, Olivier
From: Maxim S. Shatskih on 20 Jan 2009 08:26 > Within a driver, is there a way to recover the physical addresses of memory > pages that are behind a user-mode buffer pointer given via an IOCTL, as an > example? The only need in physical addresses considered to be valid in Windows is DMA, and, for DMA, you should use IoGetDmaAdapter and then the adapter object methods. Declare your IOCTL as METHOD_xxx_DIRECT, then use DMA object methods on Irp->MdlAddress in the driver to build a scatter-gather list. Then feed the scatter-gather list to the hardware. -- Maxim S. Shatskih Windows DDK MVP maxim(a)storagecraft.com http://www.storagecraft.com
From: Olivier on 20 Jan 2009 08:45 Thank you, Maxim. In fact, what I need to do with the user-mode buffer (which is in fact a locked rect in a DirectX surface of sysmem pool) is to DMA-transfer it to my device, which is not natively SG-able. So what I need to do is to : 1) Pray that the actual buffer under the surface is quite contiguous 2) Recover the set of physical pages from the pointer given by surface->LockRect in user-mode 3) Manually perform as much DMA transfers needed by the physical layout of this buffer My question is thus : does the DmaAdapter object perform any DMA-related action beneath any call to GetScatterGatherList, and does it require the underlying hardware to be SG-able, or can I safely use it in combination with a custom AdapterListControl routine to prepare some kind of DMA bursts list to be handled by my driver and device? Thanks, Olivier "Maxim S. Shatskih" wrote: > > Within a driver, is there a way to recover the physical addresses of memory > > pages that are behind a user-mode buffer pointer given via an IOCTL, as an > > example? > > The only need in physical addresses considered to be valid in Windows is DMA, and, for DMA, you should use IoGetDmaAdapter and then the adapter object methods. > > Declare your IOCTL as METHOD_xxx_DIRECT, then use DMA object methods on Irp->MdlAddress in the driver to build a scatter-gather list. Then feed the scatter-gather list to the hardware. > > -- > Maxim S. Shatskih > Windows DDK MVP > maxim(a)storagecraft.com > http://www.storagecraft.com > >
From: Alexander Grigoriev on 20 Jan 2009 10:00 There is no such thing as manual DMA. If your device supports DMA, but not scatter-gather, you may need to copy data into your own contiguous buffer (IoGetDmaAdapter+AllocateCommonBuffer). Use MmGetSystemAddressForMdlSafe if you're using DIRECT IOCTL. For a BUFFERED IOCTL, the address you get is already in system address space. "Olivier" <o.antoine(a)discussions.microsoft.com> wrote in message news:A7AA185C-9FBB-47A4-AD82-908FABF6EAE4(a)microsoft.com... > Thank you, Maxim. > > In fact, what I need to do with the user-mode buffer (which is in fact a > locked rect in a DirectX surface of sysmem pool) is to DMA-transfer it to > my > device, which is not natively SG-able. > > So what I need to do is to : > 1) Pray that the actual buffer under the surface is quite contiguous > 2) Recover the set of physical pages from the pointer given by > surface->LockRect in user-mode > 3) Manually perform as much DMA transfers needed by the physical layout of > this buffer > > My question is thus : does the DmaAdapter object perform any DMA-related > action beneath any call to GetScatterGatherList, and does it require the > underlying hardware to be SG-able, or can I safely use it in combination > with > a custom AdapterListControl routine to prepare some kind of DMA bursts > list > to be handled by my driver and device? > > Thanks, > > Olivier > > "Maxim S. Shatskih" wrote: > >> > Within a driver, is there a way to recover the physical addresses of >> > memory >> > pages that are behind a user-mode buffer pointer given via an IOCTL, as >> > an >> > example? >> >> The only need in physical addresses considered to be valid in Windows is >> DMA, and, for DMA, you should use IoGetDmaAdapter and then the adapter >> object methods. >> >> Declare your IOCTL as METHOD_xxx_DIRECT, then use DMA object methods on >> Irp->MdlAddress in the driver to build a scatter-gather list. Then feed >> the scatter-gather list to the hardware. >> >> -- >> Maxim S. Shatskih >> Windows DDK MVP >> maxim(a)storagecraft.com >> http://www.storagecraft.com >> >>
From: Olivier on 20 Jan 2009 10:28
Alexander, This - extra copy to common buffer - is especially what I need to get rid of, for performances reason, because I am dealing with very high throughput data (around 600MB/sec) and noticed a serious bottleneck around some host PC ram accesses when doing such copy. On the other hand, my IOCTL is a buffered one but I use it to pass a control structure to my driver. This structure notably contains a pointer to a locked DirectX surface, which I think is still in caller app context although the control structure is copied to system address space as you stated. Thanks, Olivier "Alexander Grigoriev" wrote: > There is no such thing as manual DMA. If your device supports DMA, but not > scatter-gather, you may need to copy data into your own contiguous buffer > (IoGetDmaAdapter+AllocateCommonBuffer). Use MmGetSystemAddressForMdlSafe if > you're using DIRECT IOCTL. For a BUFFERED IOCTL, the address you get is > already in system address space. > > "Olivier" <o.antoine(a)discussions.microsoft.com> wrote in message > news:A7AA185C-9FBB-47A4-AD82-908FABF6EAE4(a)microsoft.com... > > Thank you, Maxim. > > > > In fact, what I need to do with the user-mode buffer (which is in fact a > > locked rect in a DirectX surface of sysmem pool) is to DMA-transfer it to > > my > > device, which is not natively SG-able. > > > > So what I need to do is to : > > 1) Pray that the actual buffer under the surface is quite contiguous > > 2) Recover the set of physical pages from the pointer given by > > surface->LockRect in user-mode > > 3) Manually perform as much DMA transfers needed by the physical layout of > > this buffer > > > > My question is thus : does the DmaAdapter object perform any DMA-related > > action beneath any call to GetScatterGatherList, and does it require the > > underlying hardware to be SG-able, or can I safely use it in combination > > with > > a custom AdapterListControl routine to prepare some kind of DMA bursts > > list > > to be handled by my driver and device? > > > > Thanks, > > > > Olivier > > > > "Maxim S. Shatskih" wrote: > > > >> > Within a driver, is there a way to recover the physical addresses of > >> > memory > >> > pages that are behind a user-mode buffer pointer given via an IOCTL, as > >> > an > >> > example? > >> > >> The only need in physical addresses considered to be valid in Windows is > >> DMA, and, for DMA, you should use IoGetDmaAdapter and then the adapter > >> object methods. > >> > >> Declare your IOCTL as METHOD_xxx_DIRECT, then use DMA object methods on > >> Irp->MdlAddress in the driver to build a scatter-gather list. Then feed > >> the scatter-gather list to the hardware. > >> > >> -- > >> Maxim S. Shatskih > >> Windows DDK MVP > >> maxim(a)storagecraft.com > >> http://www.storagecraft.com > >> > >> > > > |