Subject: Re: [PATCH V2 3/6] powerpc/powernv: use one M64 BAR in Single PE mode for one VF BAR

From: Wei Yang <[email-masked]>
Date: Fri, 7 Aug 2015 09:48:18 +0800

On Thu, Aug 06, 2015 at 08:07:01PM +1000, Gavin Shan wrote:
>On Thu, Aug 06, 2015 at 05:36:02PM +0800, Wei Yang wrote:
>>On Thu, Aug 06, 2015 at 03:20:25PM +1000, Gavin Shan wrote:
>>>On Wed, Aug 05, 2015 at 09:25:00AM +0800, Wei Yang wrote:
>>>>In current implementation, when VF BAR is bigger than 64MB, it uses 4 M64
>>>>BAR in Single PE mode to cover the number of VFs required to be enabled.
>>>>By doing so, several VFs would be in one VF Group and leads to interference
>>>>between VFs in the same group.
>>>>
>>>>This patch changes the design by using one M64 BAR in Single PE mode for
>>>>one VF BAR. This gives absolute isolation for VFs.
>>>>
>>>>Signed-off-by: Wei Yang <[email-masked]>
>>>>---
>>>> arch/powerpc/include/asm/pci-bridge.h     |    5 +-
>>>> arch/powerpc/platforms/powernv/pci-ioda.c |  180 ++++++++++++-----------------
>>>> 2 files changed, 76 insertions(+), 109 deletions(-)
>>>>
>>>>diff --git a/arch/powerpc/include/asm/pci-bridge.h b/arch/powerpc/include/asm/pci-bridge.h
>>>>index 712add5..8aeba4c 100644
>>>>--- a/arch/powerpc/include/asm/pci-bridge.h
>>>>+++ b/arch/powerpc/include/asm/pci-bridge.h
>>>>@@ -214,10 +214,9 @@ struct pci_dn {
>>>> 	u16     vfs_expanded;		/* number of VFs IOV BAR expanded */
>>>> 	u16     num_vfs;		/* number of VFs enabled*/
>>>> 	int     offset;			/* PE# for the first VF PE */
>>>>-#define M64_PER_IOV 4
>>>>-	int     m64_per_iov;
>>>>+	bool    m64_single_mode;	/* Use M64 BAR in Single Mode */
>>>> #define IODA_INVALID_M64        (-1)
>>>>-	int     m64_wins[PCI_SRIOV_NUM_BARS][M64_PER_IOV];
>>>>+	int     (*m64_map)[PCI_SRIOV_NUM_BARS];
>>>
>>>It can be explicit? For example:
>>>
>>>	int	*m64_map;
>>>
>>>	/* Initialization */
>>>	size_t size = sizeof(*pdn->m64_map) * PCI_SRIOV_NUM_BARS * num_of_max_VFs;
>>>	pdn->m64_map = kmalloc(size, GFP_KERNEL);
>>>	for (i = 0; i < PCI_SRIOV_NUM_BARS; i++)
>>>		for (j = 0; j < num_of_max_VFs; j++)
>>>			pdn->m64_map[i * PCI_SRIOV_NUM_BARS + j] = PNV_INVALID_M64;
>>>
>>>	/* Destroy */
>>>	int step = 1;
>>>
>>>	if (!pdn->m64_single_mode)
>>>		step = phb->ioda.total_pe;
>>>	for (i = 0; i < PCI_SRIOV_NUM_BARS * num_of_max_VFs; i += step)
>>>		if (pdn->m64_map[i] == PNV_INVALID_M64)
>>>			continue;
>>>
>>>		/* Unmap the window */
>>>	
>>
>>The m64_map is a pointer to an array with 6 elements, which represents the 6
>>M64 BAR index for the 6 VF BARs.
>>
>>    When we use Shared Mode, one array is allocated. The six elements
>>    represents the six M64 BAR(at most) used to map the whole IOV BAR.
>>
>>    When we use Single Mode, num_vfs array is allocate. Each array represents
>>    the map between one VF's BAR and M64 BAR index.
>>
>>During the map and un-map, M64 BAR is assigned one by one in VF BAR's order.
>>So I think the code is explicit.
>>
>>In your code, you allocate a big one dimension array to hold the M64 BAR
>>index. It works, while I don't think this is more explicit than original code.
>>
>
>When M64 is in Single Mode, array with (num_vfs * 6) entries is allocated
>because every VF BAR (6 at most) will have one corresponding PHB M64 BAR.
>Anything I missed?
>
>The point in my code is you needn't worry about the mode (single vs shared)
>As I said, not too much memory wasted. However, it's up to you.
>

If we don't want to save some memory, how about just define them static
instead of dynamically allocate?

>I'm not fan of "int (*m64_map)[PCI_SRIOV_NUM_BARS]". Instead, you can replace
>it with "int *m64_map" and calculate its size using following formula:
>
>	sizeof(*pdn->m64_map) * PCI_SRIOV_NUM_BARS;
>
>	sizeof(*pdn->m64_map) * PCI_SRIOV_NUM_BARS * num_vfs;
>
>>-- 
>>Richard Yang
>>Help you, Help me

-- 
Richard Yang
Help you, Help me