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cxl: Add kernel API to allow a context to operate with relocate disabled

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cxl devices typically access memory using an MMU in much the same way as
the CPU, and each context includes a state register much like the MSR in
the CPU. Like the CPU, the state register includes a bit to enable
relocation, which we currently always enable.

In some cases, it may be desirable to allow a device to access memory
using real addresses instead of effective addresses, so this adds a new
API, cxl_set_translation_mode, that can be used to disable relocation
on a given kernel context. This can allow for the creation of a special
privileged context that the device can use if it needs relocation
disabled, and can use regular contexts at times when it needs relocation
enabled.

This interface is only available to users of the kernel API for obvious
reasons, and will never be supported in a virtualised environment.

This will be used by the upcoming cxl support in the mlx5 driver.

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Ian Munsie 2016-05-06 17:46:36 +10:00 • committed by Michael Ellerman
parent 3c206fa77a
commit 7a0d85d313
5 changed files with 34 additions and 2 deletions
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3
drivers/misc/cxl/guest.c
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@ -617,6 +617,9 @@ static int guest_attach_process(struct cxl_context *ctx, bool kernel, u64 wed, u
{
pr_devel("in %s\n", __func__);
if (ctx->real_mode)
return -EPERM;
ctx->kernel = kernel;
if (ctx->afu->current_mode == CXL_MODE_DIRECTED)
return attach_afu_directed(ctx, wed, amr);